Several situations add hit points of damage to a DC, which makes many checks impossible at higher levels when enemies do higher damage:
1. Spellcraft check to avoid losing a spell when taking damage
(DC = 10 + points of damage taken + spell level)
2. Fortitude save to survive a coup de grace
(DC = 10 + damage dealt)
3. Combat maneuver attack roll to succeed in spite of damage taken from the provoked AoO
(DC = 15 + the target's CMB + damage taken)
At high levels, damage dominates the DC equation, making other factors like spell level insignificant. A first level character can be dropped from full HP to 1 HP and still hope to succeed, but a higher level character who loses only a third of their full hit points is faced with the impossible. Since HP are abstract, there should be enough scaling so that enemy damage potential does not outpace character save and check bonuses.
I propose that instead of damage, we use scaled damage: Divide damage by one plus one fourth total character level (or hit dice). I think this bit of complexity is a fair trade for the degree of brokenness it fixes. So at 4th level damage is divided by 2; at 8th level damage is divided by 3; at 12th level damage is divided by 4; at 16th level damage is divided by 5; and at 20th level damage is divided by 6. This doesn't change the amount of damage taken, only the effect it has on DCs. I'd also like spell level to play a greater role in situation #1 above, so I'd use (2 x spell level) instead of spell level.
For example, if a 12th level caster takes 28 damage while casting a 4th level spell, the DC to avoid losing the spell is normally 42, practically impossible. Using scaled damage (28/4 = 7), the DC is 25, much more reasonable in spite of doubling the spell level.
I actually like that it cn be impossible to do some things if you let the massive face eating thing beat on you.
In a fantasy game of magic and heroes I think we should stop and think again when we see the word "impossible". I agree some of these DCs should be difficult. For example, I'd like to see coup de grace start with a base DC of 20 instead of 10. But my point is that at high levels, what used to be high damage no longer represents (necessarily) massive face eating damage. In my example, 28 damage is not a devastating blow to a 12th level character.
I favor the way it is now. A coup de grace for example is someone literally walking up to a helpless character and slitting their throat. It's ridiculous to say "I'm a heroic character and therefore should not be killed by this!" I understand the desire to want to play a heroic campaign that isn't crippled by fear of death, but at the same time there *MUST* be the risk and concept of mortality.
Similarly, a spellcaster has so many advantages, particularly as levels rise and damage scales as you mention, that the risk of losing a spell due to a well-timed blow simply has to exist. If all an AoO entailed ws sucking up a stray hit of HP damage and still getting off your spellcasting action, then there are no more tools left in the toolbox for non-casters to disrupt and stop a casting opponent.
Leave this system alone. Backwards compatibility is losing its focus what with all these suggestions for "improvement".
I favor the way it is now. A coup de grace for example is someone literally walking up to a helpless character and slitting their throat. It's ridiculous to say "I'm a heroic character and therefore should not be killed by this!" I understand the desire to want to play a heroic campaign that isn't crippled by fear of death, but at the same time there *MUST* be the risk and concept of mortality.
Then why allow a saving throw at all? I'm not trying to take away the risk of death, just make it the same across all levels. Why should it be easier for low level characters to survive coup de grace than it is for high level characters? If the math I used to scale the risk is off, I don't mind someone fixing that.
In my example, 28 damage is not a devastating blow to a 12th level character.to a 12th lvl mage/ sorc it is, Approx 1/2 to 2/3 of there hps, depending on system used.
I was assuming that 28 damage is 1/2 of a 12th level wizard's full hit points. To a 1st level wizard, the same 1/2 would be about 4 damage. Same percentage, but the DC rises by 28 insead of 4. Obviously broken.
Take a wizard with +1 Con bonus, so 7 hp at 1st level and 56 hp at 12th level. Imagine that the 1st level wizard casting a 1st level spell is hit for 6 damage. Dropped from full hp to 1 hp, his DC to avoid losing the spell is 10 + 1 + 6 = 17. Assume that the wizard has 1 rank of Spellcraft (class skill +3) and a +3 Int bonus, the total bonus is +7, so a roll of 10 or better succeeds. Not bad odds (55%) for a devastating blow.
Now imagine that the 12th level wizard casting the same 1st level spell loses the same percentage of total hp (6/7), dropping from full hp to 8 hp from a blow dealing 48 damage. If the system scales well, the wizard should have at least a 55% chance to succeed (a 1st level spell is easy for a 12th level wizard). Actually, the DC is 10 + 1 + 48 = 59. Impossible. With the formula I'm proposing, the DC is 10 + 2 + 12 = 24. Assume that the wizard maxed Spellcraft (12 ranks) and improved his Int bonus to +4, the total bonus is +19, so a roll of 5 or better succeeds. Admittedly, I didn't want the odds (80%) to be quite that good. If the wizard were instead casting a 4th level spell, the DC is 10 + 8 + 12 = 30, so an 11 or better succeeds (50%). So the 12th level wizard avoids losing a 4th level spell almost as well as the 1st level wizard avoids losing a 1st level spell. I don't think my proposal is way off.
So let me propose a correction: I'll cut the scaling factor in half, so the divisor increases by 0.5 rather than by 1 every four character levels. That means doubling the damage first, then dividing by two at levels 1-3, by three at levels 4-7, by four at levels 8-11, by five at levels 12-15, by six at levels 16-19, and by seven at level 20. The chance of beating a caster ought to hold up better that way. Again, this doesn't change the amount of damage taken, just the effect it has on DCs.
So, for the 12th level wizard to avoid losing a 1st level spell in the above situation, the DC is 10 + 2 + 19 = 31; with a +19 bonus, a 12 or better succeeds (45%). For a second level spell the chance drops to 35%. For a 3rd level spell it drops to 25%, and for a 4th level spell it drops to only 15%. This is still worse than the 1st level wizard's chance to avoid losing a spell in equivalent circumstances, but it gets us back into the realm of reasonable possibility.
If a 12th level wizard loses half his total hit points (28 damage), the DC to avoid losing a 4th level spell is 10 + (4x2) + ((2x28)/5) = 10 + 8 + 11 = 29. Assuming a +19 bonus, that's success on 10 or better (55%). A 1st level wizard losing half his hit points (4 damage) would have a similar chance to avoid losing a 1st level spell: DC = 10 + 2 + 4 = 16. Assuming a +7 bonus, that's success on 9 or better (60%).
Also magic is becoming dominating by that lvl, so it's not 'punishing' the caster for getting hit it's giving none casters a chance to actually beat a caster :p
I'm trying to maintain the same chance to beat a caster at high levels. If you really like impossible DCs for 12th level casters, then they should be impossible for 1st level casters as well. You could just say that any damage automatically disrupts a spell.
Ahh 2ed magic rules how I miss them :p
I'm not familiar with the 2e magic rules. Anyway, thanks for reading. I hope you get the gist of what I'm trying to do, even if I didn't do it very well. This appears broken to me, even if people like the way lack of scaling "corrects" what happens at lower levels by eventually making the things they don't like impossible. Or maybe damage at higher levels doesn't really grow as high as I'm assuming.
If anyone else has noticed this problem, I'd love to hear how you reconcile or work around it in play, especially if you have a solution that's simpler than mine.