I think most agree that hp is kind of a weird video game like concept. When reading a D&D style novel for example the characters aren't just taking blow after blow to their health bar. They're avoiding blows and when they are hit it hurts. The D&D sort of mechanic isn't very realistic and doesn't really fit with how most fantasy settings are actually described. Uber Warlord Killsalot isn't going to just be able to ignore a spear going though him no matter how tough he is.
While thinking about that I've stumbled across a fairly simple idea to tweek the existing rules to make them much more "realistic" and "gritty". While my idea would tone things down I'm not sure how it would play out. So I thought I'd share my thoughts here and see how you think this might effect things.
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For hp at 1st level you'd get max HD(6,8,10,12)+Con mod as normal. From there I was thinking you'd just get +1 hp/level. That kind of puts wizards on the same footing as fighters though. So instead as you level you'd get a number of additional hp equal to your BAB. Your Favored Class bonus could not go to hp and the Toughness Feat would of course only add a flat +3 hp. So a 10th level fighter for example would have 10+Con modifier+10(Base+Con+BAB) for about 24 hp total.
This would go along with some sort of armor as DR system (to decrease damage/increase survivability) and a leveling AC bonus (as high attack bonuses don't do much when everyone's AC is lower). Maybe adding your Reflex Save bonus to AC so that the dodgey classes are actually good at dodging. /shrug Anyways! This would further makes taking and avoiding blows more realistic.
Even with armor and a decent AC how would any one survive with such reduced hp? Well simply by reducing damage by the same relative amount. In every damage type situation you'd change additional dice to a flat plus to be added to the base die type. If it's a +1/level type thing then you'd just drop the plus all together. So a 10th level fireball would do 1d6+9 damage (base die type +1 per additional die).
This means a 10 level fireball against a 10th level fighter would have about the same relative effect (of loosing about half his hp) as is the standard rules. However that farmer impaling the warlord with a spear, while not killing him outright, would still hurt and would not be something so easily ignored.
While this is pretty simple and straight forward for PC types I'm still trying to figure out how that would change monsters. Even with massive DR an adult red dragon with 35 hp is an odd thing to get used to.
I didn't mind how the hp system worked when I accepted the fact that mid level characters are pretty much super human, and high level to 20th level characters have more in common with gods rather than real life people.
Ya that's kind of why I was thinking this. I'd really like levels 1-10 to represent normal humans. With 11-20 being for the heroic super human types.