With so many dice, I think you would either have to reduce the at will capabilities, or make any dice used over the first stay burned until a long rest. Otherwise at 5th level, your fighter is doing [w] + 3d8 per round at will damage. Even if you factor magic, it seems like that just moves the problem from linear fighter / quadratic wizard to quadratic wizard / cubic fighter. I guess arguably the fighter wont get AOE but I'm not sure that's enough of a damper. Even using your progression it's still 3d6 at will, half as much as the rogue sneak attack which is already a bit overpowered in my opinion.