For me the problem isn't schools of magic, it's specific spells, for example the one that consumes imbued stacks in sky magic is almost useless, one it eats up action economy, and two those imbued stacks also replace your mp.
also warrant is near useless, because it means you can't use purge as often. and most of the damage mitigation comes from countersighns rather than sanction,
Thought this is still a pretty decent game, and more importantly it's a single player game, balance is important in multiplayer games but in single player well eh.