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

Major Vikhr and Player Nezhite don't necessarily need to develop Dark magic to defeat the Orcs, since the Undead are not strong in either defense or attack, but there are many of them, and it's better to take Summoning and Light.

I don't understand the logic.

Mines will disrupt Rage.

Mines are a terrible thing against Orcs. There are only wyverns and one archer (Cyclops don't count; they shoot poorly). But once the Orc reaches them, they become useless.

Divine Vengeance will do the rest.

No, unfortunately, it won't. Vengeance, note, only attacks one stack at a time. Not to mention that the spell itself is masochistic. You need to suffer losses for it to become effective. And the Orc will crush the Undead easily. Neither House nor Vengeance will help here.

Well, you'll put a Berserker on a Cyclops.

Why on a Cyclops? I'd rather control Executioners; consider one attacking stack already neutralized, and Orcish units rarely reach you (and if the Necromancer develops tactics, they definitely won't reach you). You can use Executioners to attack Centaurs or Cyclops. It's not very pleasant, though. And Shamans aren't that scary. Goblins are a separate matter, but still, the chance that they will deflect the spell is not very high.

You're saying funny things; most likely, many of you just haven't played on a large map against the Orc.

You shouldn't make such harsh and unfounded statements.