Pyromancer

Pyromancer specialize in dealing fire damage and setting things on fire.

Fireball is one of their signature abilities, dealing damage in a small AoE. It has decent range making it good for dealing with packs of enemies before they can get close.

Incendiary Ray is strong when used in a choke point. If the enemies all line up through a single corridor, one ray can hit many enemies at the same time. It can hit allies as well however, so make sure they're okay with it before you start blasting.

After dealing Fire damage, you can spend an RP to set people on fire. While using it against a single enemy may not seem like a worthwhile trade, as RP is generally more valuable, disrupting the actions of a boss type enemy by lowering their AP by 1 can still be valuable. When using mana to use it against multiple enemies, it becomes a more appealing choice. Especially since grunts lack AP to begin with, meaning they will spend half their AP on removing the burn. If they choose not to remove it, the burn is likely to kill them after their turn ends.

The Secret Art: Pyroblast is a heavy nuke. Where most of these types of hard-hitting abilities basically require the target to be out of RP, pyroblast has a second use condition if an enemy decided not to remove the burn you put on it. If neither of the conditions are met, it's probably best to wait.