I really really think you could upgrade this build with some good pyromancing abilities as you will be int char anyway ->using supernova gives you huge aoe burst on top of phoenix dive fires, combined with fireball/ignition and topped off by spontaneous combustion (deals damage based on remaining turns of burning).
Basically you could have about 5-6 high aoe-high damage spells in row. Just have a backup plan for fire immune
Elemental affinity could probably help greatly with that aswell
