What seems over powered in it? Is it dodgy wordings for certain things like being able to exploit the class features for infinite xp and gold? I belive I have fixed it all now.
The way it is worded it means you can, but don't have to.
Note the bolding and underline added by me.
Craft was a rather silly oversight of me.Infusing the Arcana:(Su)
An Artytheurge can infuse their spells with infusions. Anytime they cast a spell that is from the transmutation spell school or another "buff" spell with a target of personal or allies, you may use any Infusion that you know,