I haven't encountered many enemy Wizards, bar Skeleton Conjurers, yet. Do they like summoning things later in the game too?
I was thinking that Anti-Magic Sphere would stop an enemy Wizard from casting any spell for a duration. You'd cast it on a boss monster or, if there are a few too many smaller Wizards about you could supress some of them to help even the odds.
Speaking of Spellshield, what is the difference between that and Aura of Guarding?
Would it be a good idea to let your Mana rise above it's max because of the spell? I think it would be more likely that you head would explode from more magical energy than you could contain!
I think Mana Restore makes sense. A pure Wizard character relies on magic too heavily to be denied it.