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

In my opinion, 3 Pain Lords is a utopia. If there's only one city with a Dark Guild, it will be problematic to find all the spells. And with a Pain Lord, it depends on the situation. Maybe a devastating ray will drop in the guild? Then what prevents learning plague from the liches? Although, in my opinion, the most effective mass spells against orcs are: weakness, slow, and dispel. The last one loses some of its effectiveness with the presence of resistance, but it can still be useful. Plus, the Pain Lord will allow you to "curse" more effectively. And with high spell power, the spell becomes a good support, especially closer to the end of the battle, when the advantage is on the opponent's side. Fire lands will reduce rage, of course, but when there are many troops in the stack, the effect will not be impressive.