the drop pools have been diluted Now by putting the pains and all kinds of ''rare'' frags that can be bought from the in game shops. before 4.0 it was fewer rare ninjas in the pool and you would get on average luck 2-4 WB asuma each week, the rarest frags before 4.0 dropped were sage naruto and hashirama I think. Basically it was easy as hell to get WB asuma from ST by just doing the 5-6 Breakthrough trials at the end, and he had a higher drop chance too for some reason cp drops were rarer then WB asuma frags.