Cool! Since I don't have a lot of time, I'll start by saying I like your designs so far. And follow up by saying that if you're fighting five wizards, you're going to want some area effect/multi-target spells. I mean, your single-target game is good, but this if this guy's trying to lone gunslinger a whole firing squad, he either need more constant/passive defenses, or much wider offensive powers.

Anyway, that's enough half-baked vagueness on my part! Here are some suggestions, for you to take or leave as you please.

Neutralize Compound: Acid spells cast by target cannot corrode substances; all acid damage dealt is prevented. Curse-type, lasts until removed.

Lightning Rod: Target attracts all electric spells that could feasibly target it, diverting them from their intended target. Curse-type, lasts until removed.

Sublimate: Cold spells cast by target fail; non-magical fog cloud emerges from their position instead. If spell was of 3rd level or higher, creates non-magical stinking cloud instead, due to low oxygen content.

Expire: Target's next sonic spell fails. Instead, they are dealt 1d8 bludgeoning damage, and are silenced for one turn, as the spell.

Unreality: All spells with an elemental descriptor in an area function as though they were 1st-level spells. (This mostly affects save DCs.)

Dark Matter: Target receives 1d4 damage, no type. Damage cannot be resisted, reduced, or ignored. Does not require line of effect to function. Does not function across planar barriers.

Achroma: Self-only. Can ignore elemental damage from all sources for one turn. Standard action cast time. Turns self - skin, clothes, eyes, everything - solid grey, colorless save for lighting conditions, for the duration.