It's pretty hard to say unless you tell us what you use it on. Open Wounds works wonders in melee duels where you hit each other once in a while, such as Zeal duels and WW duels. Deadly Strike is generally better if you already have fairly high physical damage since it doubles the damage, but it doesn't work with Smite. Crushing Blow is awesome against targets with high life since it takes off a certain fraction of their remaining life, so it works well against melee druids and barbs, and against bosses in PvM.