What 4E did was to take a hard stance, that HP were definitely just a game element that didn't signify anything deeper about how the world worked, and force everyone else to either take it or leave it. I don't think the designers necessarily realized how many people would see that as a deal-breaker.
I mean, 4E's stance is basically AD&D's stance. PCs don't actually have all that survivability, they just use luck+skill+divine influences to survive impossible challenges. It is the last few hp that represents actual dying potential(1E paraphrased). Monsters kind of have that too. Even Smaug gets hit by a lucky arrow shot by essentially a 'PC' archer — but it in part represents that all the attacks being aimed at him wore down his luck to the point where he could be killed by one shot.
You're much higher level than an opponent, that luck+skill+divine influences that they have is irrelevant, similar to what happens when say a novice fights a sensei at a dojo or a sensei fights a world champion class martial artist. Or in particular, you're a spellcaster firing off a save or suck spell at a lower level opponent who then is out of the combat vs a martial having to chew your way through their block of hp one by one.
4E goes a small step further in a sense that it says basically, we don't actually know if someone whose hp say they're dying is actually dying or not. We can only know if they were dying when they actually die. Maybe they're just nonplussed for a few seconds, lying on the ground, and in the heat of combat, who really has time to check if they're bleeding out or have the wind knocked out of them? That concept allows for martial healing — Warlord shouts at the 'dying' PC to stop acting stupid and get back into the fight. And then they weren't dying — we know this because they're now obviously not bleeding to death. It also allows for martial PCs to being equivalent to casters — we don't have to work out how the paragon tier martial PC one-shotted the Ogre in the exact same way we never had to work out how the 14th level Wizard basically took the Ogre out of combat by making it fail a saving throw in other editions.
As for falling — if an Ogre falls 10' and kills himself in a paragon tier adventure, that's fine. That means he was likely hit by a PC's attack, failed a saving throw to avoid falling, and then fell. At that much unluck, who cares if he dies or not given he's not particularly important to the encounter, likely at best about 1/16th of the XP.