Many spell effect require to mark the target with the token for the [de]buff it recievie.
If we need to book keep which unit is under which effect, then why not make the effect pernament?
the 4+ difficult buff spell that increase chance to hit by +1 is very potent! You could f.ex. double amount of hits(&wound) for very poor units! or make your elite, faultless on 2+ to hit.
I would say change it for +1 Attack dice, but make it pernament. I think it could event Stack. Buy multiple cheap Wizards, and add +4 attacks to the unit, every turn!
think about it, Wizard cannot cast same buff on 2x heros at once, but its fine for him to enchant each blade for 20 warriors?
if we instead give +1 dice attack to unit, then its more sensible.
Dispelling doesnt seem to occur very often. Because your Wizard need to see the opponent, and sacriface his casting opportunity next turn, and still its doubious that he prevent magic.
If buffs or debuffs are pernament, then you might spend your casting turn trying to remove the spell effect after, when there is no job for you wizard. It should increase the useabilty of cheap caster.