I was thinking, would it make sense to completely remove the Orcish magic resistance skills?
Instead, create a single, unified skill based on Education called Resistance (+10/20/30% to health), and add three branches to it: "Weakening" (level 1) and "Corruption" (level 2) for Light, Summoning, and Darkness. There's no need for "Sustain" skills, as they duplicate the functionality of the general "Distraction" skill from spells.
However, this would mean that, in addition to their racial skill, Orcs would only have 8 skills (they also don't have Education), 3 with 20%, 3 with 12%, and 2 with 2% chance.
Why did this idea come up? Because of the decision to abandon specific skill bans (I believe this mechanic is flawed because it requires investing too many levels in it) and to avoid creating unnecessary complexity by inventing all sorts of random effects for the 4 empty skills.
I agree that leveling up resistance to specific magic for an Orc isn't as effective as leveling up magic for another faction – they will benefit in any case, while the Orc will only benefit if the opponent has leveled up the corresponding magic (which is uncertain in the early game). But removing four skill branches seems a bit much. Perhaps it would be better to make the magic debuff skills more compact (i.e., not distribute them across 6 perks, but fit them all into 3), but at the same time, add new perks to each branch that would be useful for the Orc, regardless of what the opponent is leveling up. For example, in the Light suppression branch, add a perk that gives the hero the ability to remove harmful effects from the unit at the cost of absorbing a certain amount of Fury. Or, for example, in the Summoning branch, add the ability to summon tribal spirits that will increase the Blood Fury level by 1 for one turn without gaining Fury points.