For certain races, it's definitely very good. But for Elves...

And I leveled up Faelan with Chaos instead of Light in the campaign. And I don't regret it. There are 3 sworn enemies in each battle with heroes. Hail of Arrows, charged with Meteor Shower or Earth Shock, gives 3 decent spells per turn at the beginning of the battle, as long as the sworn enemies are alive. And with an enchanted ballista, an Elf can cast 6 Chaos spells per turn without a Mastery Amulet. There will be enough mana for everything. It turns out to be a Chaos mage even better than a Warlock. Only in the 4th mission, I would have preferred to have Light instead of Chaos.