Someone needs to read more closely. The cap as it is being discussed is a WORN attack cap, and is closer to 200. This includes worn auras(not clicked auras), vengence, and procced avatar(from primal weapons, not the spell). All spells, songs and clicky effects can stack to infinity(I dunno what your rogues sit at, but ours hit 1600attk on raids)
Actually, 250 is the worn attack cap. You cannot get more than 250 attack in worn effects like Vengance and the aura lines. Unfortunatly, this includes procced Avatar.