You know, I'm pretty sure the massive damage rule has been around since at LEAST 2nd, if not 1st, edition.
I've personally consistently operated a house rule where hitpoints only determine whether you die, not how horribly maimed you can get. You can even survive decapitation, albeit briefly, before the continuous HP loss from massive bleeding kills you. However, being decapitated does severely limited your choice of actions to something like "flop around uselessly" and "make gagging looks with your face".