Firstly, you can enhance the "Fist" and "Swarm" spells. "Swarm," in particular, is already a very good spell due to its ability to push enemies back on the initiative scale, and if its damage is slightly increased, it will be a spell that no one will be ashamed to use alongside arrow storms. "Fist" can be made a higher-level spell (although I'm not sure what to do with the first-level summoning spell then).
I have an idea that positive spells could be applied to arrows and fired at your own units. Then it would be great: cast "Phantom" on an arrow and, boom, you have three or four phantoms. And this tactic wouldn't be completely overpowered, as your own units would suffer.