MutantHamster said:
Better able to avoid damage? I tought that was dexterity?
(sigh)
Yes, dexterity lets you avoid damage, inasmuch as it increases your reflex saves and AC. You are thinking in rather concrete terms, whereas HP are abstract.
HP gains by levels are more representative of an accross the board effect of luck, skill, and sheer heroism (or "script immunity," if you will) than they are of sheer toughness.
Think of your typical action movie. The hero is getting pursued by the thugs, and the thugs miss every time. A bullet hits the concrete next to the hero's head, or where it was a moment ago. Is it because the hero is doing some fastastic sommersaults? No, usually not. It's usually blind luck and what is often referred to as "script immunity." The author intends for the focus character to survive. And likewise, typically the D&D game intends the PCs to survive.
Now you could do this in other ways that would be more viscerally satisfying to you, but the thing that makes HP mechanics work is that
1) They work with a fair degree of consistency, and
2) They work rather simply.
If you want to increase the lethality of your game considerably* and/or complicate the game to satisfy your visceral desire to avoid the abstraction that HPs represent, then by all means do so. But do so conscious of what the mechanic really represents, because from your post here, you clearly don't.
* - Not that there is anything wrong with more lethal games if that is what you and your players want, but it is not the typical D&D paradigm.