I can say that I've had a 4E combat recently in which a player only did not get reduced to negative bloodied value because a monster rolled low on the damage dice of their AoE attack. It can happen, it's just rare except in the case of a CDG.

My response to Mearls' article is basically what certain people are saying in the comments: if you want a "simple, easy, scalable mechanic that tackles these issues" in regards to healing, hit dice, and death, why not use a mechanic that is all of those things: healing surges? The numbers could use some adjustment (probably much less surges per day in Next), but they do generally work. You might need to boost HP a little to make them more meaningful to lower HP characters, but it sounds like they may be doing that anyway.

Ideally, I'd like to see monster accuracy and damage go up along with player HP. Right now combat seems too much like a missfest on the part of the enemies with the rare hit now and then that can be either crippling on low HP characters or a moderate inconvenience on a hill dwarf fighter with toughness.