The Crimson Binome
Hero
That's an interesting theory, but it doesn't really get at the underlying problem, which is abundant out-of-combat healing.To be fair, this isn't really an issue with waiting to heal people until after they've dropped. It's entirely an issue with 5e not providing proper healing spells that can outpace damage. Like, what's the point of running into melee and healing someone for a 3d8 boosted Cure Wounds when the enemy is probably doing at least that in damage each round?
This edition is (nominally) based around the theory of attrition, where you're supposed to get worn down over the course of six fights, so that not every fight needs to be a battle-to-the-death in order for it to matter. Except, due to the excessive availability of out-of-combat healing (hit dice and resting, in particular), that doesn't really hold up in practice. You never really go into a fight with low HP, even near the end of the day. And the response to that is for the party to conveniently face much tougher monsters, who are capable of eating through your overly-generous HP allotment in a single encounter, because any encounter that can't potentially kill someone has zero consequences.
If you get rid of hit dice, and you slow down natural healing to a reasonable rate, then you don't need to fight monsters that can deal damage faster than you can possibly heal it. You can go ahead and fight a monster that only does ~20 damage per round, even if you can Cure for ~30 with a single spell, because healing-per-round would no longer be the limiting factor in over-all survival.