Balance in Heroes 5.

That's absolutely true! As everyone knows, Necromancers are currently the weakest... but they are numerous... and more people play as them... although no amount can compare to quality!

The fact that they are the weakest is a deliberate provocation, "like, take an undead army and play without Necromancy, and then you'll feel their weakness."
Yes, that's how it is, I don't argue.
But, you can also say, take a Wizard and play without a spellbook, and so on.

Added after 17 minutes
No offense to anyone! But balance is a... murky... thing.
I think it's unpleasant when the Castle you like ends up in the category of weak Castles.
Otherwise, play as whoever you want, and choose a Castle (that is inconvenient for your opponent). Although, in theory, you can win with any Castle against any Castle.
Because, in addition to the standard strength of the Castle (~40%)
add ~30% luck (good fortune) and ~30% the skill of the player, and you get the result.
THE PROPORTIONS ARE CONDITIONAL, JUST FOR CLARITY!!!