I only recently started doing PvP to kill time between crafting. (10 hours KI? come on!) It's a fun way to kill time. I am a lvl47 theurgist - haven't finished grizzleheim or dragonspyre. I think I have defeated a wizard of every school except balance. I always get my behind handed back to me on a platter. Storm lords come a close second, because of that tricky wild bolt. Life against life can last FOREVER.
I am slowly learing strategies against each class, but you balance wizards.., I can't touch you! Honestly, I am not really complaining. Just chit chatting. It's all still very fun. As long as the opponents take it all in sport too. Don't judge me! :-P
Balance has all those spells for attack and the spells that make the opponents attack weak. I've managed to beat Balance, but they seemed like they didn't know what they were doing. The experienced balance players would but buffs and such and then kill me with Judgment.
Balance can be tough, but it's Life that gives me the most trouble. The only way I've been able to defeat them (in 1v1 against equal or higher level) is to outlast them. Sometimes they'll run out of attack spells. That means you need a deck that holds a lot of cards and has a few heals in it. This same tactic helps against Balance, too.
Balance has one advantage and two disadvantages. Their advantage is that there are no regular shields against Balance spells, so you have to rely on Tower Shield or absorbs. The disadvantages are that their spells do kind of low damage and most of their bread-and-butter attacks (spectral blast, hydra) are elemental. So put up lots of fire, ice and storm shields against Balance.