Ok,
I was just reading this thread and it occurred to me a problem with this sort of thing a friend of mine had. He was telling me this, so It might not be accurrate, but basicely it seemed to him he was playing two people at one. He was using a water poison, and one of them was a mono darkness (i think). He thinks they all took turns to attack each other, and so sometimes half his creatures would dissapear, as one would attack him, while he was against the other. He could only talk to one guy, who could also see the third guy, but not talk to him. In the end, as his poisen cards poisened both of them double, he beat the first guy, and the game stopped.
Sorry this is a bit vague, but I can't quite remember - it was some time ago.