View Full Version : Simulating Wounds with HP?

Mr. Mask
2015-11-18, 10:06 PM
Some games have HP, and some games have Wounds, and many games have both. Stereotypically, losing HP is fine, until you lose your last point, at which point you drop like a rock. Wounds, on the other hand, tend to come with penalties, and sometimes specific effects (like losing an arm meaning you can't wield two-handed swords).

One thing I wondered, was whether you could do a decent job of simulating wounds through HP. I've heard of a couple of games where you get penalties at reduced HP, but haven't gotten to look at them closely.

What are the pros of cons of having penalties for reduced HP, vs. more specific wounds? Anyone with some experience in such able to comment?

The main trouble I've seen, is it can be annoying to calculate how many missing HP means how much penalty, especially if magical healing is available.

2015-11-18, 10:38 PM
Loss of HP can be displayed as:

- Signs of physical exertion such as raggedness of breath, slacking movement and posture or slight staggering and shaking
- Inconsequential wounds such as small cuts, bruises and abrasions
- Coughing up blood or bile
- Dented/dislodged armor, or other skin-deep damage such as chipped claws or a few missing scales
Can't think of more right now but thats the idea

Why these things don't actually affect mechanics can always be explained. For example if this guy is so exhausted, sweating and bleeding why isn't he slowed ot have a penalty to hit/damage? His adrenaline and desperation is keeping him going. Alternatively, he actually is weakened.

2015-11-18, 11:19 PM
Perhaps you could implement certain HP thresholds which simulate different levels of injuries? Like, once below 50% max HP you are Bloodied. Bloodied imparts some sort of penalty and sometimes a bonus. Ex: Barbarian who gets bloodied now has a penalty to checks to resist things like disease or physical restraints, but they get to reroll damage dice and take the highest values. Once a character is below 25% they are Wounded, suffering harsher penalties and perhaps gaining greater advantages. Like, that same Barbarian now suffers 1HP loss per round, but auto-rages immediately and cannot die physically for 1 minute.

Mr. Mask
2015-11-18, 11:32 PM
Mm, that's the main system I've seen implemented to have wounds through HP. -X for Y increments lost. You can have helpful little rows of check-boxes or the like to help you keep track.

Of course, you can't simulate losing use of a limb or the like this way, although that could be judged as a fight-ending injury.

2015-11-19, 02:31 AM
Adding 'realistic' injuries to D&D-style inflating hit points is a path to madness. There's plenty of other systems that handle it much better.

Mr. Mask
2015-11-19, 02:37 AM
Well, they don't necessarily have to be DnD style inflating HP. It might be HP caps out at about 20 points for humans, with more damaging weapons.

2015-11-19, 02:48 AM
Wouldn't it be easier to just have different body parts, each body part has a fraction of your "total health", damage to any body part imposes a 1:1 penalty on actions that involve that body part. Take 5 hit points of damage to your right hand = take 5 points penalty to swinging a sword with your right hand.
Get to 0 points left and the body part is disabled. Damage beyond zero does not count toward total.
Get to -100% and the body part is destroyed (if it's the body or the head then you are dead).
Damage done to body parts is equally done to total, when total hits zero you become unconscious.

Your penalty is based on your damage, your health is based on something that doesn't change much rather than something that inflates. This would probably not work with a combat system like D&D where you're supposed to take 10 daggers through your face and be fine.

The benefit to using a wound system is that it makes combat seem more realistic and you get a better feel of the damage you take and inflict, it isn't just abstract numbers, you're not just getting highscore on tetris. But you'd have to want something like that for it to be a benefit and many people don't.

Mr. Mask
2015-11-19, 02:56 AM
They actually have that in a game called Kenshin.

My only concern is that with say the legs, you use your legs in swinging, defending, etc.. Same for the torso and head, really. So it's hard to say whether a wound to the legs should effect your swing or not, and how much if so.

2015-11-19, 03:05 AM
For very high adventure games I think the advantage of HP is that it is easy. Whenever wounds/hit-locatione tc is introduced it requires more bookkeeping (especially for combat heavy games).

However, if you can find a good way of handling the bookkeeping (a good systematic approach at the table) and you like more "realistic" combat (like I do), then I think hit-lcocation and some sort of wound-system is really great.

Two things needs considering: is it short term or long term injury.

Short term injury:
Any serious trauma can cause shock etc to the wounded person - reducing their abilities for a short time. This can range from" stunned" over "shocked", to "passed out". Minor injuries could cause penalties to all or specific physical skills/feats/abilities or whatever the game have, while average injuries could cause the loss of turns/rounds/actions or whatever the game have, while major could cause blackouts and the removal from action.

As the shock from the injury wears of the combatent regains full ability (even if still carrying the reduced HP). This way injury have a serious in game affect and you cannot just ingore large amount of damages since "ohh.. I still got plenty of HP", but at the same time the player is not reduced permanently from action or feats.

Long term injury:
I think this part is best implemented if some sort of hit-location system is also in effect. It can increase tactical decisions of the players (aim at the legs to demobilize opponents). The area/limp injured is disabled: ranging from numb and useless for a short time, over broken/injured you cant use the limb for a few months (or until healed), to cut off - only magic regeneration (or hyper advanced surgery in a Sci-Fi) will make it better.
It can either be calculated as a fixed amount of damage (X1 damage stuns your arm, X2 brakes it or cause major injury, X3 makes it permanently damaged) or if the HP system allows for more HP a certain percentage of the damage (40% of HP damage in one attack cause temporary loss of function, 60% of HP damage a long term one and 80% of HP the loss of the limb permanently).

Questions: Is it in order to make your own system or in looking out for systems worth playing/modifying? GURPS have some injury system, that includes both short term stuns and more permanently loss of limbs etc.

2015-11-19, 03:10 AM
I'd like to suggest that perhaps the location of the wound is not as significant as the effect it incurs. Meaning that distinguishing between damage dealt to specific areas is superfluous if you can simply keep track of damage until the next wound, and how many wounds may be suffered before incapacitating the character.

Maybe what you need is a simple damage track, which when a threshold is exceeded, incurs a random affliction upon the character until that damage is healed.

If the next threshold is crossed, another, more severe, infliction is incurred. This one can be cured, but not in a dungeon / battlefield and will require real medical attention.

If a third threshold is crossed, then a permanent infliction is incurred. This level of damage should end the current fight and incapacitate the character, but not necessarily kill them. They could recover from it, but it'd take a lot of rest and medical aid.

At this point, you should decide with your group how lethal you want the game to be. How many third tier injuries should be sustained before a character is either crippled or killed.

All this system would need is three short tables, one for each damage threshold to determine what penalty is inflicted after an injury.

2015-11-19, 03:57 AM
The main problem with including threshholds in a system like D&D is that it adds a big chunk of bookkeeping. The single 'bloodied' one of 4e is fine, you just need to check wether you're above or below, but putting one every X% of HP will cause you to triple-check your sheet every roll or fail to read it correctly most of the time. And don't get me started on tables.

And then it occured to me that 3.5e D&D already has a (relatively) simple wound-like system of weakening someone during a fight that scales with level and have rules for recovery : negative levels.
You need to rework the way HP scale so it doesn't explode first, but that's not too difficult. Then, every time your HP are depleted, you gain a negative level and reset your HP. Damage carry over. You can keep a major damage rule from a hit that cause several wounds at once, but you don't die from HP loss anymore.

2015-11-19, 04:58 AM
In my homebrew system, the Stage (currently being tested here (http://stage-rpg.com/)), we use a wound system.

Characters have Stamina points and Vitality points. Stamina points can be used to absorb damage and losing them has no negative consequence; they are also used to fuel certain powers. Once a player has run out of Stamina points, damage is subtracted from Vitality points and the player incurs a wound that causes him to lose a die on all skill checks (the Stage uses a dice pool system). There is a similar system for Intellect and Sanity points (used to fuel mental abilities and absorb mental damage), and Will and Spirit points (used to fuel spiritual abilities and absorb damage to the soul).

The advantage of this system I find is that is that players get an incentive to lay off when they're about to die: penalties limit effectiveness in combat and players tend to withdraw once wounded. It also adds an extra dimension for bards/barbarians/doctors (converting wound penalties to bonuses in a heroic last stance or rage or adding value by being able to heal wounds).

The disadvantage is that it's not very 'bespoke' to the actual attack: this wound system is not based on where a character is hit; they just receive a penalty that the GM will have to link to the wound by describing it.

In general, my biggest concern with wound systems is that they tend to introduce a level of realism that may not always be fun in role-playing games. A character having to spend weeks (or months) recovering from wounds after a battle, is usually not very interesting from an RP perspective :smallsmile:

If you're using D&D, I've used a house-ruled version of the HP-threshold described by Ninjadeadbeard; it works remarkably well, but getting into more detailed wound systems is too much administrative work, I find.

2015-11-19, 05:08 AM
Long term injuries in D&D?

Best system I ever saw used reduced max HP as a primary function and used a table for descriptive mods.

So let's say a player gets critically hit. 1 point per charlevel HP becomes locked into the injury. Then you roll on the injury table for the descriptive effect of head trauma or whatever with disadvantage on perception and knowledge checks. Until the HP is healed, the penalty persists. Natural healing, from long rests, restores 1/4 of the lost HP. Magical Healing works normally.

2015-11-19, 05:08 AM
Wouldn't it be easier to just have different body parts, each body part has a fraction of your "total health", damage to any body part imposes a 1:1 penalty on actions that involve that body part. Take 5 hit points of damage to your right hand = take 5 points penalty to swinging a sword with your right hand.
Get to 0 points left and the body part is disabled. Damage beyond zero does not count toward total.
Get to -100% and the body part is destroyed (if it's the body or the head then you are dead).
Damage done to body parts is equally done to total, when total hits zero you become unconscious.

That's pretty much how Runequest does it - getting into fights without armor in that system is a good way to commit suicide. An axe-blow to the head will settle almost anyone's hash. (Instead of higher HP, more experienced combatants are better at not getting hit.)

White Wolf's Storyteller/Storytelling system uses an abstract set of Wound Levels that fill up as you get hurt, with set dice-pool penalties on everything the worse hurt you are. Like a hit-point system, but with more coarse-grained resolution.

A common way is to throw out hit points altogether, and just use individual 'wounds' as penalties (either stacking or just taking the most severe) on most/all rolls. Savage Worlds does that, as does Silhouette. (Both systems use fairly small numeric ranges (1-12 in SW, 1-8 in Silhouette), so even a -1 penalty is a big deal.)

Legends of the Wulin takes a more narrativist approach - injuries, poisons, curses, and emotional problems are ALL statted as 'Chi Conditions' which give you a penalty for not playing along worth it ('broken leg', 'broken heart', 'poisoned with Red Adder venom'). There's also beneficial chi conditions, but you generally don't get those from a fight.

2015-11-19, 05:12 AM
There's a few different ways that I've seen this applied fairly well - none of which involve D&D style increasing HP. The big ones are having actual boxes for HP and just ticking them off and looking at what section of the HP track one is in for penalties, having HP and also a wound penalty based on individual injuries (whether it's something like greatest single injury, a quantity of generic wounds, or whatever else), and the Fate Stress-Consequence system, where you have a limited pool of HP, but HP depleting attacks can be bounced off to injuries to some extent.

Wouldn't it be easier to just have different body parts, each body part has a fraction of your "total health", damage to any body part imposes a 1:1 penalty on actions that involve that body part. Take 5 hit points of damage to your right hand = take 5 points penalty to swinging a sword with your right hand.

The 1:1 penalty idea only works with very specific dice systems, but health distributed through body parts is nothing new. It's often pretty clumsy, and often adds another roll, but there are cases where it's done quite well. A good example of this is the ORE system, which incorporates hit location into one roll fairly simply, and has everything inflict both shock and killing damage (other than things like unarmed combat being only shock). If a limb fills up with shock, it gets effectively useless. If it fills up with killing, there's generally some sort of permanent injury.

Joe the Rat
2015-11-19, 10:14 AM
Marrying wounds and wound penalties directly to D&D style hps works best if wounds are reflected by a proportion of the total, rather than by direct numbers. When you hit thresholds (1/2 hp, 1/4 hp, < 1 HD, 0), you impose flat penalties, or take a roll on some sort of short-term or long term wound table, depending on how low they go. There is an option in the Palladium system along these lines, and the D&D 5e wounds options could be drafted to this purpose. Just remember to be an equal opportunity penalizer. In essence, this turns your hit points into your "stamina/body" pool for wound levels. Storyteller or Shadowrun, only with buckets of numbers instead of buckets of dice.

Another way to do this is to have wounds and hit points be independent functions. Getting beat up causes hit point loss, but it takes something special to cause a wound. This is how Rolemaster did it. your "hits" are concussion damage - getting badly bobbled by body blows. When you hit 0, you're knocked out. It's easy to get hit damage - even the toughest armors against their poorest weapon matches will take hits from relatively low rolls. But real damage - wounds with impact, and potential fatality - came from criticals. This is what armor was for - raising the thresholds and lowering the severity of the criticals, and their consequent wounds. Pulls and sprains leading to penalties, deep cuts causing you to bleed out, broken limbs, hurting movement and defense... and a few amusing instant death effects, which you might want to skip for your system. Part of the way this worked was by criticals coming at flat number thresholds rather than specific die results. You don't critical on a "natural 20", you "critical" on a 20 or more, with higher rolls invoking worse effects.

Of course, part of how this worked was that the penalties were tied to the specific injuries, and healing hit points does not heal injuries. There was separate treatment and healing times for those - and separate spells for repairing different types of injuries (Organ Ways for those ruptured spleens and missing eyeballs, Bone Ways for, well, bones, etc.). For a D&D style, you'll need to cook up recovery times, and possibly new spells (or put Restoration and the like to the task) to fix up the wounds.

2015-11-19, 10:20 AM
You could do a relatively simple approach and "lock" HP at certain wound levels. Say a player has 100 HP. If they get down to 75, they cross the first threshold, and cannot be healed above this threshold by any means before they treat the wound (with a special spell or a medicine check). This way you have little bookkeeping, but wounds can still have an effect,

Mark Hall
2015-11-19, 11:21 AM
SAGA and Hackmaster both use wounds in interesting ways.

Saga has a condition track, which imposes penalties as you move down it; some attacks go after the condition track directly, while very large attacks may damage the condition track in addition to HP.

Hackmaster has a concept called the "Threshold of Pain." The Threshold of Pain is, whenever you take a single hit that does that amount of damage or more, you must make a "Trauma Save". Succeed, and you're ok... damaged, but still standing. Fail, and you're down for 5 seconds for every point you failed by... or several minutes if you roll a 20. Threshold of pain is 40% of HP for monsters, 30%+1% per level for non-fighter PCs, and 30%+2% per level for fighter PCs; your trauma save is usually rolling under 1/2 your Con on a d20, though there's an expensive trait to reduce that to a d12.

Additionally, each wound heals separately in Hackmaster, going down in size 1 point per days equal to the current size of the wound... so if you have ten 1 point wounds, you're fine the next day, whereas a single 10 point wound will take you 55 days to heal (10+9+8+7+6+5+4+3+2+1), unless you have magic, or someone with First Aid training to make sure you heal more swiftly.

2015-11-19, 12:24 PM
One option is to apply a sort of "status effect" on a player. Maybe if they are down to 1/4 HP, they are limited to a move or attack, but not both. But it's something I'd talk about with players before I implemented.

2015-11-19, 02:15 PM
Shadowrun does it. Characters get wound penalties for taking damage. In practice, it's really easy to tell what penalty you should be taking. As for pros and cons, some people like to complain about death spirals, but that's the point. Being hurt means you don't fight as well as normal. Even excluding wound penalties, it's a highly lethal and unforgiving system, in keeping with the feel of the setting. In shadowrun, getting shot is a very bad thing, being caught in a grenade's blast is pretty much instant death, and in serious playstyles it's expected that players will attempt to achieve their goals without violence.

For permanent wounds in an hp system, I like ACKS mortal wounds table. Whenever a character gets KO'd, a roll is made to determine how badly injured he is, and what lasting effects occur, if any. It's modified by things like how tough the character is, how much damage he took beyond what was needed to KO him, and the quality of medical care he received. And it has a diversity of effects, from purely-cosmetic scars, to losing eyes and fingers, to being reduced to an unrecognizable bloody pulp.

Mr. Mask
2015-11-20, 10:56 PM
One system worth mentioning, come to think of it, is Banner Saga. In it, your health score is also your damage/attack score. So as you get to low health, your amount of damage decreases. It's an interesting idea.

A friend of mine is keen on the idea of each HP lost is a -1 to attack rolls, with about 20 HP being the most you can have. I was wondering if having to regularly change penalties would be a problem. I guess that might be worth starting a thread about, managing multiple changing penalties.

2015-11-21, 08:09 AM
In Alea Iacta Est (http://www.topsecretgames.net/wp-content/uploads/2014/05/Alea-Iacta-Est.pdf) you take a penalties once you have 40 or fewer hit points, and every 10 below that, regardless of whether you started with 45, 50 or 55 (so your first 5-15 hit points are your buffer). I'm currently working on a system which uses both hit points and wounds - you take a wound and return to full HP each time you reach 0 HP.

2015-11-21, 01:37 PM
In GURPS you're at half Move and Dodge when you're under 1/3 your HP or FP (fatigue points). You can also suffer crippled limbs - damage over ... either one third or half your HP (I forget which it is, my group has mostly been going for headshots lately) to an arm or leg cripples it (and further damage to the limb doesn't subtract from your HP, but can severe the limb). Hands and feet also have a cripple threshold, and the eye cripple threshold is 1/10th HP.

2015-11-22, 09:04 AM
With out a doubt my favourite heath system I have ever seen is War Machine's Warjack heath grid. It does require an extra role to assign damage but you have a really nice system that direct damage, which tied to causing wounds, is still partially independent from it. The only problem is it requires a static grid with has all your heath system. More amendable to a role-playing game is Hordes' Warbeast health spiral, which is also used in the role-playing game variant of both, Iron Kingdoms, or so I've been told.

Both systems essentially work by having "parallel" health tracks were damage is applied to one at random, extra damage flowing onto the next one. When all boxes of a certain type are marked, the character suffers a related injury. Also how the health tracks are laid out is not uniform, so some injuries are more likely to occur on different characters.

I would describe the whole thing in more detail but that would probably take an essay.

Lvl 2 Expert
2015-11-24, 05:24 PM
Perhaps you could implement certain HP thresholds which simulate different levels of injuries? Like, once below 50% max HP you are Bloodied. Bloodied imparts some sort of penalty and sometimes a bonus. Ex: Barbarian who gets bloodied now has a penalty to checks to resist things like disease or physical restraints, but they get to reroll damage dice and take the highest values. Once a character is below 25% they are Wounded, suffering harsher penalties and perhaps gaining greater advantages. Like, that same Barbarian now suffers 1HP loss per round, but auto-rages immediately and cannot die physically for 1 minute.

Alternatively have a few thresholds (60%, 30% and 10%), roll a die when you cross a threshold for the first time in a day or when you take some definition of massive damage. Each result corresponds to a body part/functionality. Say 1,2 = arms, most skills and attack, 3,4 = legs, movement, 5 = body, constitution and armor class, 6 = head, mental stats. If you roll a body part ones you're lightly wounded. You get a small penalty to the functionality it represents. This wound automatically heals when a healing spell or potion is used on you (or when you get to over 60% health again or something) or when you've had a long rest (or even a short one). The fun begins when you roll the same part again before getting healed. You get a moderate wound. You can heal the wound back to a light wound, but without a healing spell of a certain level cast on it or a healing check of a certain DC it will stay a light wound until after a long rest. A critical wound has even worse effects and some more rules on how you can and cannot restore it, and with a massive wound you lose that functionality completely. The next day you will still have a moderate wound (except when exposed to some powerful specialized healing) and it will always leave some sort of scar.

It's kind of complicated, but it could work alongside hitpoints.

2015-11-24, 06:04 PM
They tend to work better where you have a 'buffer' between your actual HP (lifepoints etc). The first larger pool is the buffer which has to be chewed through before you're actually hitting them and taking out lifepoints. Possibly a crit can bypass the buffer pool. (The old Star Wars Revised d20 had such a system. Didn't work especially well for that game - but they had it. :P)

Basically - the buffer pool represents your protagonist/heroic awesomeness keeping you from actually getting hit, while the lifepoints is actually being hit, and being low on lifepoints does give negatives.

It doesn't really work well in D&D, because D&D HP is a combination of the two.

2015-11-25, 01:01 AM
I like Savage Worlds damage system and Wounds.

Your Toughness and Armor prevents all Damage Effects, if the damage inflicted is less than your Toughness and Armor. Every Wildcard (PCs and important NPCs) has 3 Wounds. You get Wounded if the damage is four higher than your Tough+Armor. You get a penalty to all rolls that corresponds to the number of your Wounds (even -1, at your first Wound is pretty bad). When you get Wounded the fourth time you are knocked out, become Incapacitated and you need to roll to see if you get non-permanent or permanent Injuries or Die. This is simple because everyone gets damaged the same way, with equal numbers. Some characters may even have special rules when it comes to suffering damage and Wounds and none of them is: "The characters adds +1 to his Wounds.".

There's also a form of minor Damage Effect that only really causes momentarily shock (or something similar) in the form of Shaken-condition. If the damage received is equal to your Tough+Armor you need to roll to recover on your next turn or you lose your turn. If you do recover, there are no lasting effects. You're also more easy to Wound if you are Shaken.

NPCs who are not important die if they suffer just one Wound.

Sure, it's no exactly realistic but that's because the system aims to be cinematic. For example, at three wounds you have -3 to everything and it is a horrible condition to be in. Especially so, if you are constantly expected to risk life and limb in new and interesting ways. Death lurks very near when you are at three wounds. Yet... you are in no danger to bleed out, even if you were wounded three times with a sword.

Lvl 2 Expert
2015-11-25, 01:06 PM
I'm currently working on a system which uses both hit points and wounds - you take a wound and return to full HP each time you reach 0 HP.

That also sounds cool. It allows you to push through heroically in spite of ever worsening injuries. Your character will be useless for two weeks afterwards (or fine the next day, depending on the rules), but you did it (or not of course, and now you're powerless to stop things).

Fosco the Swift
2015-11-29, 12:05 PM
The 2 types of hit points seems popular. Unearthed Arcana (D&D 3.5 supplement) has a Vitality and Wound HP system based on the Star Wars Roleplaying Game. Pages 115-119. I've never tested it, but it seems to work well enough.

the OOD
2015-11-29, 05:34 PM
I strongly recommend looking at the Universal Decay system, a beautiful d20 system that makes both mechanical and realistic sense, and plays like 3.5 amazing with internal consistency*.

vitality represents endurance/physical energy, and is wis mod+ con mod+ one die per level (lost when sprinting, taking damage, performing hard labor, ect.)
HP is exactly what it sounds like, and is con score + 1/2 BAB. (only scales slightly with level, higher level means that a character is more skilled, not superhuman)

at half health, a character suffers penalties to move speed and d20 rolls, at 1/4th health, these penalties are increased
at half vitality, a character suffers penalties to move speed and d20 rolls, at 1/4th vit, these penalties are increased (stacks with HP penalty)

if you take more damage than your con score in one hit, you make a fort save vs damage taken or suffer special damage (broken bones for bludgeoning, blood loss for slashing, ect.)

* the system makes total sense, and you rarely experience a divide between common sense and mechanics.(heavy Armour makes you harder to hit, but doesn't decrease damage taken? what the hell, 3.5?) also, it has enough internal consistency that you can use the fantasy setting with the robots and nanites from the space setting without needing to introduce any new rules. totally. freaking. compatible.

2015-11-29, 08:34 PM
What are the pros of cons of having penalties for reduced HP, vs. more specific wounds?

I can't speak to more specific wounds (i.e. wound locations) because I haven't toyed around with them much.

Penalties for reduced HP, be they offensive, defensive, or both, have different impacts depending on whether you are fighting a single creature or fighting several. In D&D, where there are no penalties until 0 HP, the best strategy is usually to focus everyone's attacks on the single most threatening opponent until that one drops (adjusted for massive differences in defense), then move on to the next, etc.; this reduces the total DPR of Team Monster fastest, and thus preserves the most possible of your party's HP. Introducing penalties can change this in different ways, depending on what is penalized:

Offensive penalties give the wounded party a reason to cut and run if and only if their opponent does not have the same penalty. It makes getting the first major blow extremely important, so you'll want to load up your buffs and use your biggest guns right out of the gate. If you're successful, your opponent is now less likely to be able to retaliate in kind. If both sides are paying attention and playing aggressively, the combat is largely determined in the first round. However, when you're fighting multiple opponents of roughly equal threat, it decreases the pressure to focus fire until each opponent is dead, because other opponents are now more of a relative threat than the wounded one.
Defensive penalties have a different problem. Once an opponent slips into defensive penalties, they become an easier target than they were before. This is the exact opposite of the offensive penalties and so encourages focus fire; the threat is the same, but the payoff is even greater. Another difference is that just because one party slips into penalties first, that doesn't mean the outcome is determined; the wounded party is still just as capable of inflicting penalties on the non-wounded party as before. That creates a decision point for the wounded: do you try and knock the non-wounded guy down to your level, or do you cut your losses and run for safety, and how likely are you to be able to escape your opponent if you do?
Penalties to both: Once your opponent takes both offensive and defensive penalties, he's less of a threat and he has every reason to run away. First blood is again of paramount importance, because you are less likely to come back from that in both ways. This is good for fighting swarms of goblins, who you want to take a licking and then run away so you can focus on the next wave, but it's bad for the PCs, because fights are largely determined by the half-way point (or whatever point you start inflicting said penalties), so you just run and hope your enemy lets you go.

To recap: offensive penalties make combat more deterministic but decrease focus fire pressure; defensive penalties make combat less deterministic than offensive penalties, but increase focus fire pressure relative to offensive; and offensive/defensive penalties make combat as deterministic as offensive alone and may or may not decrease focus fire pressure (depending on other opponents' relative threat and defense). Of the 3, penalties to both seems most problematic to me, while penalties to defense only seems the most manageable. But if you're doing that you have to ask yourself what you're really gaining over having no penalties at all, since the strategy doesn't change (focus fire on the biggest threat until it's dead, rinse, repeat). You've essentially just shortened combat, is all.

What you want to do is decrease focus fire pressure without determining the outcome by placing the first wounded adversary at a permanent offensive disadvantage. So what if it were a temporary penalty instead? You hit 1/2 HP or whatever threshold, and you are Shaken or something, where you take a -5 (or analogous) to attacks, but either take no defensive penalty or a very small one. To overcome Shaken-ness, you have to spend a turn neither attacking nor taking damage and make one or more appropriate saving throws (or analogous). After that the penalty goes away and you're back in the action. That way, the wounded adversary has the incentive to retreat, and the non-wounded adversary has the incentive to let them do so and shift focus onto another target unless there isn't one, in which case you have a hunter-hunted situation, where if the hunted can manage to get a chance for a quick breath, they're back on an even playing field. This doesn't close the door on more permanent consequences; you could still get a max HP penalty until your injury is properly treated, for instance.