Nonsense. The issue with having severely overpowered units & spells is that they limit game options. If I'm playing as Trogs, I can either use Juggernauts, which completely steamroll every AI and quest, or deliberately play sub-optimally to gimp my faction (as in, either avoid building them or deploy them poorly). I could also decline to play as the Trogs altogether. None of these options is particularly fun or conducive for game immersion.
The developers don't need to nerf everything powerful in the game. They could buff existing content which is too weak (like summons) or add new counters (like a weapon or spell which does increasing damage to a unit based on the target's weight). But something has to be done, or the game will devolve into a dichotomy of playing The One Right Way or tying your own arm behind your back.
End of Bobchillingworth's quote
Nonsense. You say all this like people haven't been playing the game, and winning, on all difficulty levels without playing as Trogs since release (and long before, really). There is no One Right Way and to suggest one exists is asinine. Play the way that is fun to you. I've played probably 6 games to completion since release and only one used Juggs. And in only one other was a Juggernaut based faction a threat to me.
To claim that Juggernauts are the only proper way to play the game is ludicrous. By midgame my Adventurous Betrayer Sovereign who has stolen the souls of nearly every free hero he has recruited in order to gain easy spell levels oneshots armies of Juggs with one spell before they can move. Clearly, that one spell is overpowered and anyone not playing my preferred way is gimping themselves, tying one arm behind their back, and failing to play The One Right Way.
+1 to anyone who can guess the one spell.
That doesn't mean that other play styles don't need some love. They certainly do. However the love they need isn't "balance", it's distinction.