Well if it will make you feel any better the Lull line & Harmony line don't seem to take hold on ANY mob (works fine on players but not on mobs) with the current 6.4 server either.
Took a look at the spells_us.txt file and its listed as a Benifical buff which if you take that off it will just make the spell only good pulling
Maybe its not taking hold because mobs are not allowed to be buffed with player spells ATM?