ramzes, have you seen how much mana "Subjugate" consumes? Let them use it to their heart's content. What's the problem?
It consumes 45 mana – not that much. The duration is 2 turns! This will cause my own cyclops to attack my own warriors: a reduction in army strength, and the cyclops won't attack the enemy for two turns. In those two turns, the undead will have time to significantly damage the panthers, for example, by attacking them with the same cyclops. And the main damage is dealt by the mass attacks of the panthers and cyclops. So, "Subjugate" is actually the problem.