Tonuss has great Arena multiboxer fairness logic!!

In BGs, I have a huge advantage because I can move 4 little dots on the map at once, strategically, without having to convince/cajole my teammates to follow me. I can decide, "Hey Me, let's go cap Lumber Mill", and then do that because I'm going to move there and I have enough characters to be able to beat the 3 defenders. I get a lot of the advantages of a premade (coordination) without having to have one.

Shamans are interesting because they mitigate a couple, but not all, of the multiboxer weaknesses. Even so, a skilled player or group of players can take a multi-shaman team out if they use their brains or (gasp) work together to exploit the weakness.