But with the spellcasting skill and spells enhanced by 50%, chaos seems to help units quite well.

In contrast to the warrior-focused knight, it might be worth introducing a magic-oriented warlock, but something tells me that these wouldn't be entirely equivalent heroes - the warlock is much better with magic, and the difference in stats gained with levels wouldn't be very noticeable. I'm afraid that almost everyone would choose him in that case.

My idea regarding warriors/mages was to replace some of the standard stat boosts on the map with their own, with a choice of attack/defense/magic/knowledge, so that you could take even more control over the leveling process.