As an elvish vampire, I took fifteen or so followers to kill a bandit. It went surprisingly well and the bandits were slaughtered.
Being a vampire, I decided to sate my bloodthirst on an unconscious guy laying there.
That was when I discovered that companions apparently drop out of your party when wounded or something.
My entire entourage immediately attacked me. I shot several of them, bashed a couple to death with my bow, then fenced another with my left hand while choking a lasher into unconsciousness with my right. I killed the swordsman, dropped the lasher, then went after a couple of macemen. I killed them, then went after the last guy, a crippled crossbowman.
As I advanced towards him, the Lasher suddenly regained consciousness, stood up, and killed me with a single blow to the head.