I realize this discussion has been going on forever, but perhaps I can offer a new perspective. I teach some self defense stuff, so I've learned a bit about what it takes to stop a human attacker. There are essentially two ways to stop an assailant: physically incapacitating them (either through blood loss or destroying a vital part of the central nervous system) or by hurting them enough to persuade them to stop attacking you (a psychological stop). Self defense tends to emphasize the first method, because the second isn't a sure thing. Your assailant may be on drugs, or adrenaline, or just really determined.
This is what I think differentiates minions from heroes and non-minion NPCs. A hero has the psychological wherewithal to keep fighting even when he's injured. As long as he can physically keep fighting, he's going to do so. Same with non-minion NPCs. Minions, on the other hand, are not made of such stern stuff. As soon as they take a solid hit, even if it's not life threatening, they turn into a gibbering wreck. If they have the intelligence and willpower to actually do something, all they'll be doing is trying to staunch the bleeding and bind up their wounds.
The key is to think of what happens below 0hp differently for a minion than a non-minion. A non-minion with negative hit points is unconscious (or dead). A minion with negative hp may be unconscious or dead, but they may just be lying there in shock, or sitting there staring at his wound, or trying to staunch the flow of blood. They're both out of the fight, but one had to be physically battered into submission while the other was a wimp who gave up on the first hit. It's their psychological durability, rather than their physical durability that differs.
