You took Valeska, and the enemy has the infamous Fortress and Bron. What's next?
You took Valeska, and the enemy has the Citadel and Tiraxor. What's next?
You took Valeska, and the enemy has the Conflux and a hero with Luna. What's next?
In my opinion, the variability in such a game is still very good. And if you add random castles and random heroes... then you'll probably have to make the map more complex to compensate for the local imbalance.