Question about level scaling vs monsters

[soulsabre345]

I'm trying to figure out damage builds for my character and I'm realizing I have no idea of what's the expected AC per level to go up against, or expected damage to do, so I'm posting to ask if anyone knows a decent formula for them. They seem to be referenced occasionally, but I haven't seen them directly.

Specifically, I want to know 2 things;
1. What attack bonus does a melee character need to hit a typical creature at a given level?
2. How much damage does a melee character need to do per round to combat a typical creature at a given level.

I do want a per-level formula, even if not perfect, so I have at least a ballpark estimate of what's good or bad per level. This is also assuming middle ground optimization, the kind of thing WOTC was assuming when designing most monsters.

Oh, and I'm interested in the pathfinder formulas as well, although I believe they are very similar.

[Zaq]

One of the many reasons that CR is such a crapshoot in 3.5 is that there's nothing even resembling a rough formula here. I'm going to leaf through the MM1 and look at some monsters in the CR 5-8 range (no particular reason for choosing that particular CR, but there are plenty of good monsters there) and just look at their ACs and to-hit bonuses. I might stop if I get bored.

Aboleth, CR 7, AC 16, to-hit +12 (4 attacks)
Gargantuan Animated Object, CR 7, AC 12, to-hit +15
Elder Arrowhawk, CR 8, AC 22, to-hit +19 (touch) or +20
Athach, CR 8, AC 20, to-hit +16 (single) or +12 (many)
Greater Barghest, CR 5, AC 20, to-hit +13 (and 2 +8s)
Basilisk, CR 5, AC 16, to-hit +8
Behir, CR 8, AC 20, to-hit +15
Belker, CR 6, AC 22, to-hit +9 (and many +4s)
Bodak, CR 8, AC 20, to-hit +6
Bulette, CR 7, AC 22, to-hit +16 (and 2 +10s)
Chaos Beast, CR 7, AS 16, to-hit +10 (2 attacks)
Chimera, CR 7, AC 19, to-hit +12 (3 hits) and +10 (2 hits)
Chuul, CR 7, AC 22, to-hit +12 (2 hits)
Cloaker, CR 5, AC 19, to-hit +8
Babau, CR 6, AC 19, to-hit +12 (2) and +8 (1)
Succubus, CR 7, AC 20, to-hit +7 (2)
Destrachan, CR 9, AC 18, to-hit +9 (2)
Bearded Devil, CR 5, AC 19, to-hit +9/+8
Chain Devil, CR 6, AC 20, to-hit +10
Erinyes, CR 8, AC 23, to-hit +14/15
Hellcat, CR 7, AC 21, to-hit +13
Digester, CR 6, AC 17, to-hit +11
Elasmosaurus, CR 7, AC 13, to-hit +13
Tyrannosaurus, CR 8, AC 14, to-hit +20
Dire Bear, CR 7, AC 17, to-hit +19/+13
Juvenile Black Dragon, CR 7, AC 22, to-hit +16
Dragonne, CR 7, AC 18, to-hit +12/+7
Drider, CR 7, AC 17, to-hit ranges from +6 to +1
Bralani, CR 6, AC 20, to-hit +11 and under
Huge Water Elemental, CR 7, AC 21, to-hit +17 (2)
Ettin, CR 6, AC 18, to-hit +12
Formian Taskmaster, CR 7, AC 19, to-hit +10/+8
Efreeti, CR 8, AC 18, to-hit + 15
Hill Giant, CR 7, AC 20, to-hit +16
Gibbering Mouther, CR 5, AC 19, to-hit +4 (6)
Flesh Golem, CR 7, AC 18, to-hit +10
Gorgon, CR 8, AC 20, to-hit +12
Gray Render, CR 8, AC 19, to-hit +15
Green Hag, CR 5, AC 22, to-hit +13 (2)
Six-headed Cryohydra, CR 7, AC 16, to-hit +8 (6)
Invisible Stalker, CR 7, AC 17, to-hit +10 (2)
Lammasu, CR 8, AC 20, to-hit +12
Lillend, CR 7, AC 17, to-hit +11
Werebear, CR 7, AC 17, to-hit +13/11
Medusa, CR 7, AC 15, to-hit +8
Illithid, CR 8, AC 15, to-hit +8 (4)
Mohrg, CR 8, AC 23, to-hit +12
Dark Naga, CR 7, AC 14, to-hit +7
Nightmare, CR 5, AC 24, to-hit +9
Nymph, CR 7, AC 17, to-hit +6
Ogre Mage, CR 8, AC 18, to-hit +7
Black Pudding, CR 7, AC 3, to-hit +8
Phase Spider, CR 5, AC 15, to-hit +7
Phasm, CR 7, AC 17, to-hit +12
Ravid, CR 5, AC 25, to-hit +4
Remorhaz, CR 7, AC 20, to-hit +13
Shambling Mound, CR 6, AC 20, to-hit +11
Cloud Giant Skeleton, CR 7, AC 13, to-hit +18
Red Slaad, CR 7, AC 19, to-hit +11
Tendriculos, CR 6, AC 16, to-hit +13/8
Adult Tojanida, CR 5, AC 23, to-hit +10
Treant, CR 8, AC 20, to-hit +12
Troll, CR 5, AC 16, to-hit +9
Umber Hulk, CR 7, AC 18, to-hit +11
Vampire, CR 7, AC 23, to-hit +11
Will-o'-Wisp, CR 6, AC 29, to-hit +16 touch
Winter Wolf, CR 6, AC 15, to-hit +9
Wyvern, CR 6, AC 18, to-hit +10
Xill, CR 6, AC 20, to-hit +7 (or 4 +5s)
Yuan-Ti Abomination, CR 7, AC 22, to-hit +13

So yeah. There's so much variation, and so many outliers, that it's really hard to come up with a baseline. Some of the outliers, of course, are obviously not meant to be slugging it out in melee, but that's not always the case. And this isn't even getting into monsters or humanoids with class levels.