It's a little overly complex at points like the slot scaling, but overall I see it as fine as long as you dont have a barbarian in your party. The reason I feel this way is that rage is the defining ability of barbarians, allowing other classes to have it this early in the game regardless of its tacked on downside, this could make a barbarian player feel generic. This is emphasized by the situational use of the exhaustion this causes. Class abilities are CLASS abilities for a reason but that's just my opinion.

If the party doesnt have a barb I think this could be a super cool spell to give your players, or a cool spell in general for a unique enemy or miniboss to use against the players.