Table says "School resistance" but text says "arcane resistance." Text also refers to "resistance rolls" which aren't a thing in 3.5 or PF. Do you mean saving throws?
As written, it is a bit weak against actual casters. Additional things I'd consider:
Gain evasion and mettle at some points.
Gain ability to reroll failed saves some number of times daily.
When using a dispel magic effect (either as a spell or other effect), allow them to sacrifice a spell slot to add twice the spell level to the dispel check or (or caster check if PF).
The smite ability should also cause those smited to lose spell slots or prepared spells (maybe one of highest level) unless they make a save.