1. Could you swarm the Wizard with creatures? Yeah his armor is nice but you could maybe wear him down. Especially if you managed to get rid of the Regrowth Belt. It would seem a Beast Master could get out a bunch of cheap creatures fast enough to swarm him at least at first.
Swarm is a good way to deal with the voltaric shield, but the wizard has cheap access to Mordok's Obelisk, and will probably also run a Suppression Orb. This is to say nothing of the fantastic suppression cloak, which is probably the strongest of his anti-swarm spells. The wizard is really good at control, so swarming him may be difficult.
Oh believe me I found that out yesterday lol. I managed to take out the Oblelisk and it got a lot easier but putting Essence Drain on my pet timber wolf, Mana Siphon out, and other fun stuff did not make my Beast Master jump for joy. And oh yeah that Suppression Cloak is horrifying.
These ideas were just in reference to the Watergate spell book I saw linked. I firmly believe The Wizard has the potential to take on any and all comers. I think of him as Batman, with the right plan he'll take on any threat you want to throw at him.