Well, they can always put caps on the damage to prevent a spell from becoming OP.
What I mean is, let the spell damage be boosted by "Mage Level".. or the amount of magetraits a character have, so each trait that you put in one of the ones available from path of the mage lets you deal more damage.
Putting a cap on the damage is a bad move I feel, because that would just "Worsen" the state, where mages become irrelevant to other classes.
Scaling by level is a good idea, but I think it should be refined to reflect that the mage class is the MAGE class, and each other class have access to magic, but have to rely on buffs and debuffs, and not raw magical damage, either that or only magical damage from single target spells.
Another thing you could do is let spells scale with more easily accessible items, remove the evoker traits, and give mages some WAAAAY more interesting traits, like if you removed spells ability to crit, you could make a new spelltrait that would allow each magespell to crit after you have this trait, and subsequent traits would boost this particular's mage crit chance.
Spell traits that would allow you to deal a certain amount of damage even if the creature resisted your spell, granted resisting in my head should remove ALL of the spell damage.
Stuff like that. - So many things I would have done different 
Sincerely
~ Kongdej
