1. A couple of ideas to balance it
1. Slow when cast on a bloodlusted (Ogre at least) reduces it to even damage with a paladin, instead of making them hit 1.5 times more hard instead.
2. Exorcism gets rid of bloodlust on beings that have it. Would you be for a radius-effect, or that the paladins have to cast it on every bloodlusted creature on individually?
3. Could you change healing so that it also gives the paladins a defense bonus against melee (hand to hand) damage?
4. Since it is possible to change an ability, (such as exorcism working on Ogre-mages, instead of just death knights/skeletons) have healing not heal at all and instead give a defense bonus, rename it "Holy Vigor" or something like that
Kinda like option 3, but it was give defense instead of healing as well.
5. What about just plain getting rid of bloodlust for Orcs? At least you can destroy the Ogre-Mound to get rid of Ogres (and OMs) , though destroying the Altar of Storms, won't make it so the players couldn't make Ogre mages, or cast bloodlust if they've already researched either of them.