If you can't buff/shield yourself at a moments notice, it's just a poor idea. Sure, it works in bgs games, but only because when you go into your inventory to eat 20 cheese wheels, the game outside the menu pauses, and the effects of the cheese wheel happen immediately and they stack. If any of that doesn't happen, the whole playstyle falls apart. Anything with a delay in the healing is out, so spells are usually not the solution unless you've managed to buff cast speed and either lower mana consumption or increase mana pool. If the world outside the menu kept going, you wouldn't have enough time to eat all that, if the items didn't stack, you wouldn't get enough health for a fight

It can be a fun build, but like you said, you need to be able to manipulate your HP at will, I'll never pick one of these builds in a game like, say, ARK (not that I know of any such perk in that game, just using it as a genre example), as healing out in the wild is a slow and slapdash endeavor and you're much better off building survivability over DPS (unless you're playing with a clan and one of your mates takes a strictly support role)