What skills should Necromancers take when facing Orcs on a very large map?

We were playing with a friend, I was Necropolis, and he was Fortress, on a large map. We both developed to level 30. I had twice the army size, but I barely did any damage to him with my large goblin army, and I even had better artifacts. Question: are Orcs overpowered, or what? If not, how do you fight them? They attack very often.

I don't think Orcs are overpowered; they're just a strong faction. I advise rushing them; you need to finish them off quickly before they get to Cyclops. And Darkness is effective against Orcs. Although, it's better to develop two schools of magic, otherwise, they might take Antimagic. Also, taking Cursed Lands in Darkness is essential; it greatly reduces the Orc's attack.