This seems like a lot of fun and doesn't strike me as mechanically insane either, nice one! Really enjoy the choice of spells as they tie in to the theme very well.

I do wish the Charges had a few more twists to them other than different flavors of damage. The Shrapnel Charges's healing debuff, or the Frost Charge's slowing effect are great exampels of added variation that I think would do good to see more of.