You can say the same about any Orc tactic – subjugation combined with cunning is a panacea.
This is what creates the imbalance. Either remove subjugation completely, or change it somehow, or give the Orcs a way to counter it.

Against the Orcs, Undead is truly devastating, even more so than subjugation itself. Because if there are no Undead and the game is long, Goblins can severely disrupt spellcasting, and the probability of this will increase over time. Considering the Silence spell, Cyclops become virtually uncontrollable, and other units are subjugated, but their initiative is significantly reduced, and they may not even get a turn. By the way, the 5th mission in the Orc campaign teaches this if you pay close attention; the developers did a good job. And the Orcs have their own powerful abilities, like Horde Fury and Roar, not to mention absorbing damage with a single point of Fury, which is very unpleasant if you're not playing as the Necromancer. And the Necromancer shouldn't relax either.

As for the imbalance in the other direction – who would be against removing it?
For example, stronger morale effects from different creatures or Necromancer skills, or a greater increase in meat production through necromancy in a long game, or something else that allows for strategic play.

If you're going to balance things, don't do it against the Necromancer; this vile creature will resist anyway (Berserk, Readiness + Vampirism, Converter). But what about the others without Subjugation?

And it's not necessarily the Necromancer hero who needs to go first, especially for the Cyclops.
Even one or two War Chiefs going first will significantly increase the chances of the Cyclops going first.

Without top-tier initiative artifacts, you need at least two War Chiefs to go before the Cyclops, because otherwise, the chances of the Cyclops getting two turns before the Undead Legions, which is highly desirable (because with skeletons dealing 3-4 damage, Liches, Vampires, and Messengers, and no Cyclops, what will you use to deal damage later with this tactic?), will drop dramatically.