I like the way 4e handles death itself. I like the "3 saves" thing (though I'd get rid of death at "minus Bloodied" as I don't think it's needed). I like that healing starts you off at 0. And I like that resurrection is costly, has a medium-term effect, but doesn't lose you a level.
I agree, however, that 4e isn't quite lethal enough.
3e, by contrast, is too lethal at low-levels, about right at mid-levels, and then insane at high levels (easy to die, easy to come back).
I would like 5e by default to have a Beginner tier with the "lethality dial" set to the 4e position (or slightly easier), and then the Heroic, Paragon and Epic tiers set to about mid-level the 3e position.
And, as far as possible, they should show the DM the math that makes all that work, and give him the tools he needs to adjust that lethality dial to whatever value suits. Plus, they should try really hard to encourage the DM to set the dial accordingly and then not fudge the dice to keep PCs alive!
(The talk about levels 1-4/5 for combat lethality is also good. That would tie in with encounter design, and with the notion of the DM configuring his own "lethality dial".)