Mages go pew pew!

If you can survive their opening burst damage sequence of a mage, you can beat the mage. Just keep your health high and flying with Flash of Light and watch amusedly as their mana bar empties out on you. Counterspell is a threat to you, but if they don’t hit you with it as you cast, you can just bubble out of it. If you get spell locked, the fight is over, because the mage will have 10 solid seconds to do whatever he wants to you. The longer this fight takes, the more likely you are to win. Once the mage runs out of mana, the fight is over, but it’s not going to be easy for you.