Shogun
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You say that Minotaurs need to be replaced. But where would they go? Think about it: where can Minotaurs live? (not necessarily within the setting of Heroes of Might and Magic V). Personally, I doubt they belong in a meadow, peacefully grazing and nibbling on grass... it's absurd! Originally, Minotaurs lived in caves, or rather (as has been suggested) in labyrinths. By the way, in all parts of "Heroes," Minotaurs lived in labyrinths. The Castles were simply not called Dungeon, but Warlock, i.e., named after the wizard. In my opinion, removing units from the game that have survived and thrived in all five parts of the series is, to say the least, foolish. But that's just my personal opinion.
I would even suggest replacing the Matriarch with, say, Manticoras. Their only advantage is that they shoot and cast Slow.
P.S. Dungeon is a very strong Castle in itself, and it's logical that, besides "super" monsters, it should also have weaker ones. This is where the fragile word "balance" comes into play.
Well, I understand and even sympathize with your position regarding Minotaurs, but please understand me too. Two units that are slow and none of them are flying (I never made it to the late game) + only first-level archers with a penalty to shooting = storming the Academy Castle becomes a lottery. I'm not suggesting adding another uber unit to the army, but just introducing a mid-level flying unit, which, in my opinion, wouldn't disrupt the balance.
However, introducing a powerful level 6 flying unit into the army would seriously disrupt the balance, in my opinion.