Power Buildings

There will be as much mana as the skills and artifacts provide (not counting summons), and it doesn't depend on the hero's class. Morale reacts to any other element in the army (including the hero), whether it's friendly or not, just in different ways. So, we take the Bird, level up some kind of buff skill (besides the already mentioned Combat and Tactics), and off we go!
P.S. You might get lucky and receive Dispel right away with the basic Magic of Order skill.

Skills require levels. And in the end, you'll get a barbarian-mage who doesn't have much opportunity to learn the necessary spells, relying on scrolls and books, and has lost his combat power, with which he could practically level up and acquire artifacts and resources on his own, without an army.
So, what will Dispel of Order give a barbarian? The ability to remove a curse? But then he will also remove immortality - and that's a big chance of him being destroyed.

A barbarian has a large army, even if you don't take a secondary noble, the number of troops will still be very large, so it's worth taking Tactics and leveling up Combat so that he can immediately give the army "buffs" in battle, which will only be removed after his death, and considering the armor and attack, it will be very difficult to do. And in the meantime, the barbarian can independently reduce the ranks of the enemy's troops.