Its like an amror piercing arrow? lol.
I target C but they are behind mobs A and B it hits everything it passes through to C. Its an obnoxious skill that really has no use just like knockdown arrow outdated skills that need an overhaul to be useful again, slow shot I only use in Olympiad to kite tanks. So not worth upgrading.
Bow strike is nice quick stun alternate if impact is reloading, I do use it sometimes as a 2nd stun.
So quick shot, pinpoint, impact, multi arrow, arrow rain and phoniex arrow are main skills to upgrade.