In all seriousness, a health bar going down and not coming back up unless you heal is the same thing as having it refilled after combat automatically, in terms of make-sense. Like, you get beat up, your health is at the middle and you still fight like nothing ever happened and when it's out you automatically fall? Is on/off "serious" rpg mechanic? I don't think so. Also I don't see anything Diablo-esque about health bars refilling after combat, considering in Diablo you need to heal via magic or potions.
The only thing that matters is: does this new system works well with resting mechanics? Does it give players a challenge? Everything else is monolithic traditional rpg rationale, imho. I'm a fan of split health/stamina, but, as I mentioned numerous times (even in Pillars 1 discussions), the best other mechanic I've seen in pcrpgs is the DA:O system "survive the encounter or game over and if you fell, you get injured. Get many injuries, can't progress ('cause you're gonna fall easy!) - go heal yourself" that Deadfire is heading to, as it seems.