The problem with death is not "lugging around ten trillion potions to prevent it," it's "if you fuck up at all with using them, or, say, lag for five seconds while stuck among a mob while the game actually goes through using that potion" (fuck satellite connections for gaming, seriously) - less a matter in difficulty of preventing in optimal conditions, and more a matter of how harsh the punishment is when you screw up, whether it's your fault or not.
You just stated one of my biggest complaints with MMOs and similar games. Players can recover all their HP in less than two seconds, so the only way for enemies to actually threaten players with death is to give them completely absurd DPS. This means if you get mobbed by more than one of the things or there's a lag spike or something, you're dead.
I'd prefer to see a setup where healing is much more limited and is a resource that must be carefully managed, and players get worn down over the course of a raid, rather than getting knocked to critical and healed to full every few seconds. This would also remove the constant need for a healbot, which nobody likes playing.