I would say they should be banned specifically in Zero Sum, but for the rest of the arenas, if you’re capable of creating a good tactic with decoys while sacrificing the use of a primary weapon (see: @Alexbrand – dueling grounds) then it’s fair enough. They’re also pretty invaluable for Cavern survival. About the Blue Fox, I think it’s powers should be limited. On Dueling grounds if you don’t have it then you’re at a serious disadvantage: I think too much of a disadvantage. And if you both have it it creates a lot of waiting around shooting at peasants and no-one gets an advantage at all. So I think it’s powers should be curtailed, maybe a shorter period of changing, or less health for the peasant.
I think a larger issue with multiplayer is the ‘loop’ breaks multiplayer code issue. The blue side of Dueling grounds + multiplayer treasure is practically unplayable on a large scale because of the tens of draws you get with old players on the red side; but anyway, that’s for a different topic…