It procs a 1500ish DD, non-melee that will show up as spell damage.
Re-use time is 8 seconds.
Pretty nice extra little DPS. Some minor draw-backs - it seems to be a slight bit more draining on endurance than the rest of your quicker reseting combat abilites, but not too bad (havnt had a chance yet to use it on a longer raid mob but i'd definitely see this draing you real fast). And it's on the same timer as your temple stun and tendon snare.
So, it can be used on top of your volley, frenzy and overpowering frenzy.