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

You're saying some funny things; most likely, many people simply haven't played on a large map against the Orcs. For example, WitcheR-L: "Okay, you put a Berserker on a Cyclops (although few free units are available, and they usually try to keep them away). He'll destroy half the Goblins, giving all the troops Fury. But the Orc's army isn't just Cyclops; there are also Executioners (who move very far and attack strongly), Warmongers (almost impossible to break through with Fury), Wyverns (which devour Necromancer corpses, making them impossible to resurrect), and Centaurs (which destroy all ranged units). So, I don't think it's about any kind of 'blockade'; it's better to upgrade Luck, Leadership, Logistics, and Defense!" Major Whirlwind and Player: "Necromancers don't necessarily need to focus on Darkness to defeat the Orcs, because Necromancers aren't strong in either defense or attack, but there are many of them. It's better to take Summoning and Light (Mines will disrupt Fury, and Divine Retribution will do the rest). The only problem is the amount of mana, so upgrade Education and Sorcery. Whether Necromancers can win 80% of the time depends on the map and the opponent."