Well, firstly, the combat system (even when fully upgraded) can't compete with hypnosis, mass summoning, Sanctuary, Sacrifice, which offer far greater strategic possibilities in large-scale battles. Among the creatures, only the Black Dragon provides a clear advantage, but the cost of its production and its slow production speed significantly diminish its overall effectiveness (complete immunity to all magic also plays a role).

These are my personal impressions gained during gameplay. I don't think there are any clearly defined strong or weak factions in the game (as mentioned a few pages ago); otherwise, there wouldn't be this discussion ;), and the imbalance would be obvious.