Waerloga is very hard to beat mano a mano. 

I've done it, but with a level 30 character packing very, very good gear. Ultra-high spell resistance (avoid being stunned) and resistance to criticals is almost mandatory.

I remember when he was first introduced it was a one-on-one battle, but that was also back when the dragon shrine quests were the way to quest victory.  I'm a little sad to learn that you no longer fight him solo (goes to show how long it's been since I've won via quest).