NHF – new heroes for Heroes V 3.1.

In this case, I didn't quite express myself correctly. I meant not classes within one faction, but heroes from different factions.

That's exactly how I understood it =)

That is, in my opinion, individual skill trees for different factions should take into account the stats of that faction.

This is clear and understandable.
A Mage will remain a Mage even in another class.

But I'll repeat, but in a different way, that there shouldn't be big differences within factions. For example, an Academic won't be a 100% Warrior, and if we want a Warrior, we play, for example, as a Knight.
If there were two classes within the Academic faction: a Mage and a Warrior, this would mean that they are opposites. And this shouldn't be the case, because a Warrior is a different faction, and we would lose the uniqueness of the faction.

Added 4 minutes later
For example, let's say there are an Academic and a Wizard from the Academy.
The first remains as is, the second receives a bonus to magic due to knowledge.