TriKster I think the tooltip is pretty clear, for calculating damage bonus from keen throw its always +2 shurikens from flip of a coin, so it should be 9 x 12 = 108% more damage. Its also better since its consistent.
On a side note, we dont have much sustain on this build do we? Currently i am using bleeding heart to leech health but i dont wanna give up my amulet slot for it. Any alternatives?