I disagree that the two races are pretty equal and have their own strengths and weaknesses. Pretty much one word does humans in-bloodlust. Here's a few strategies I've heard to try to beat it, not sure any of them really work well.
1. Cast slow on them............Ok, now they only do 1.5 more damage instead of 3x the damage if fully upgraded, still in favor of orcs.
2, Cast Flame shield on a paladin/paladins attacking the BL'd Ogre Mages, or cast flame shield on the ogres when they sit outside before they attack and bloodlust each other. The first one, not sure, plus flameshield also damages YOUR units, you don't want several flameshielded paladins attacking the ogres, while also damaging each other. The second one, not sure.
3. Polymorph the Ogre Mages- Ok........gonna need lots of mages fully charged with mana, maybe too many for it to be feasible.
4. Blizzard the Ogre Mages- Sure, just gonna need them to stand still long enough for you to do it, if your paladins are fighting them you'll probably hit them as well.
5. Have the paladins backed up with archers to hit the Ogres from behind. Not sure about this, how does it work? Some people have told me they only produce archers for fighting against Dragons and Griffins, not sure how this would work.
6. Outnumber the Ogre Mages with more paladins. Basically build more barracks then your opponent has. Still, since the Ogre Mages do three times the damage of paladins, you're going to need 3 times the barracks!
7. Use Griffins to hit Ogre Mages- seems good in that the OM's can't attack the Griffins, just wonder if they could kill them fast enough
8. Use dwarf demolition teams to attack the Ogre-Mages, and by the way- do goblin sappers do more damage when they explode if they are bloodlusted?
What about combining some of these. Perhaps using strategies 1+2+4 might turn the tide in your favor, or maybe not.