Hmm... good point. I'll think about how these will work, thanks!Mages already have far more than enough damage boosters and high damage/dps spells. Running out of mana to actually USE these spells is a much bigger problem. And while yes, a damage boost is nice, a mage shouldn't be getting hit where possible. You are the second frailest class in the game for a reason (not counting the joke class that exist pre-hardmode in Throwers).
Also, currently, the accessory is a nice, but not mandatory one. The moment you make it have a potential damage boost it becomes mandatory to obtain/use for the class for lategame.
Your solar boots have their own damage, yes, but no damage boost. Unless you made their damage broken overpowered, I wouldn't feel compelled to use it, as I have alternatives I could use, but if it was multiplying my own damage, that would change.