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

Here's a question about the Orcs. Why do you think the "Darkness Shield" spell is ineffective? I actually like it a lot. Firstly, it prevents Cyclops from being controlled. And that's a significant advantage! Since Cyclops are the main strength of the Orcs, and they also deal damage to two units simultaneously. Secondly, Berserk and Control can be weakened so that they only last for one turn, and the Necromancer would have to reapply them each time. And Necromancers are always short on mana, so this would be a considerable nuisance.