I also don't always LB on the first boss in AK, because we get to him quickly enough that the LB bar isn't full until a point in the fight that using it would actually be slower. By this I mean the animation for it would take longer than using the 2-3 abilities needed to finish him off, and he's dead about the time the big golem spawns anyway. Now if I could get it off in time to prevent the first guy from summoning the 2nd one (not the golem, the one that summons the golem, psychflayer I think...) then that would be great and I would definitely use it.