In RBG PvP Bloodbath+Bladestorm will outperfrom Avatar becouse their combined cd is 2ce shorter and that combo should deal dmg similar to combustion (and we all know how it hurts), besides 6 sec total cc imunity isn't something to sneeze on. In arena setting imo talent choice would depend on what setup you're playing - for example stormbolt into heroic throw is unavoidable 6 sec cc on healer, need that hard cc to prevent your druid dieing to melee cleaves - shockwave. Overall unlike for most classes we've plenty of choices to make and compared to probably all other classes we've best talent tree aviable.