So we are only supposed to play against stupid people? Even when spawned in different places, where would the fun be in that?
Also, in a past interview, the developer stated that "you could not tell the difference between single player and multiplayer because the AI is so good" so it wouldn't really matter if the bosses were being controlled by a player or computer. There are four boss zombies, and two are extremely weak, one dies with one shot, and one is extremely tough to even things out. (The extremely tough one has a control timer, so you have to strike with him quickly.)