also, it will not work if the mobs dont have at least 1 melee attack in their list of attacks. this is a pretty rare occerance, but keep you eyes open when dealing with imps, and some welplings.
Edit: also like Bodh said, but to clearify. NEITHER BoP or Devine Shield is a true agro wipe, you will get your agro lvl back upon expiration of the buff.
Edited, Feb 4th 2008 8:45am by RuenBahamut