Characters can only truly be killed by a named villian/antagonist--or, perhaps, when the death is meaningful in some way. This is actually an optional rule in 13th Age, but I like it.
I actually just finished a post on my blog about changing up the ability scores in 4e. I like the OD&D version of ability scores; how they're generated, the very low bonuses (really, no bonus to hit/damage in OD&D, I've discovered, but in Basic, I think, it was *Ability Score - 10 and then divide by 4, round toward zero*), the generally static ability scores.
I started a thread a couple of years ago asking how much changing back to that earlier paradigm would mess up the 4e math. My idea was to de-emphasize the importance of ability scores, making it less necessary to invest in having the highest primary stat in order to still be effective. The scientific consensus of the thread was that changing to an earlier style of ability score generation/use would mess 4e up pretty badly.
However, I have a hunch that using escalation die would alleviate some of the problems. But then one must figure out how to scale up the defenses, so that monsters aren't wiping the floor with the characters.