Think this through with me: slow casting

[ILM]

I've seen this houserule mentioned a few times here and I find it intriguing. I'd like to discuss it in a little more detail.

For the purposes of this discussion, let's formulate it like this (may be updated if something needs to be fixed):

All spells with a casting time of one standard action, one move action or one full-round action have their casting time increased to one round. Their effects takes place at the beginning of the caster's next turn. Casters may select targets and/or affected areas at the end of casting, immediately before the effect takes place (bad idea?).

The rule causing spontaneously-cast spells to have their casting time increased if any metamagic is applied to them is removed.

The Casting Defensively option is removed.

The Rapid Summoning Conjurer variant is removed.

The Quicken Spell feat is changed to a +2 level adjustment and lets the caster cast a spell as a standard action.

Spells with a casting time (as printed) of one swift action or one immediate action are unaffected by this houserule.
Alternatively, instead of increasing the casting time, just state that spells with a casting time longer than immediate or swift manifest at the beginning of your next turn instead of at the end of your action - in effect, you get the same results except that casters get to keep their move actions.

Thoughts? How is that likely to really affect the game? Is it abusable in any way?

[Salanmander]

It will make concentration much more valuable, and make casters think harder about where they're casting spells. In general, I approve.

Two things to consider are quicken and mirror image. Mirror image because it becomes dramatically more useful when your spells are in danger of being interrupted all the time, to the point that it might become a spell that is almost required...a spell tax if you will.

The thing to consider with quicken is how it interacts with this. I would assume quicken exists, but just reduces the casting time to a full round action or a standard action (I forget what it normally does to 1-round spells). That being the case, is it still worth +4? Almost certainly not. It might be worth reducing its modifier to +2 or +3.

[ILM]

It will make concentration much more valuable, and make casters think harder about where they're casting spells. In general, I approve.

Two things to consider are quicken and mirror image. Mirror image because it becomes dramatically more useful when your spells are in danger of being interrupted all the time, to the point that it might become a spell that is almost required...a spell tax if you will.

The thing to consider with quicken is how it interacts with this. I would assume quicken exists, but just reduces the casting time to a full round action or a standard action (I forget what it normally does to 1-round spells). That being the case, is it still worth +4? Almost certainly not. It might be worth reducing its modifier to +2 or +3.
Considering I mentioned removing Casting Defensively, I suspect it makes concentration useless, on the contrary (if you get hit, you're pretty much sure to lose your spell even with like +30 to Concentration).

Mirror Image does become perhaps more useful (as do, in general, defensive measures) but a) all the rounds a caster spends buffing himself for his own personal defense, he's not really contributing to the fight, and b) it might only encourage Dispel Magic usage, which I'm not wholly against.

I addressed Quicken Spell in my OP.

[Answerer]

That might be too much. It's not that casters aren't powerful enough to get around this, it's just that in an average game it may become unfun to deal with. Spending too many rounds doing nothing isn't much fun. And the solution to that would be damage immunity, which you probably don't want to encourage spellcasters to go looking for.

[erikun]

As I mention whenever this comes up, healing sucks under these rules. The problem isn't even that is sucks for the Cleric, but that is sucks for the rest of the party because now the Cleric pretty much cannot heal anyone in the middle of a fight anymore.

And before anyone jumps in with the "healing is sup-optimal in combat" discussion, stating that the rule works just fine if you're playing above-average optimization is just saying that it doesn't work for half the optimization levels.

[ILM]

As I mention whenever this comes up, healing sucks under these rules. The problem isn't even that is sucks for the Cleric, but that is sucks for the rest of the party because now the Cleric pretty much cannot heal anyone in the middle of a fight anymore.

And before anyone jumps in with the "healing is sup-optimal in combat" discussion, stating that the rule works just fine if you're playing above-average optimization is just saying that it doesn't work for half the optimization levels.
Fully agreed. I was, in fact, already considering a specific exemption for Conjuration (Healing) spells (either as a feat or for free, not sure yet). I forgot to include that in the OP.

@Answerer: you don't really spend time doing nothing; in fact, you still cast one spell per round. However, you can get interrupted, yes. It does encourage casters to try and become invincible, but weren't they already trying?