I've just started leveling my Priest again and currently I'd like to know what classes can a Priest beat in 1v1 and which are impossible to beat, using any spec that works best against each given class.
Nagina is right, as long as you know what skills you have at your disposal then you can effectively down any class, its also very important to know when to kite. Don't worry about Holy or Disc specs, just go Shadow, and remember that Power Word: Shield is now you besttttt friend, so keep it up when you take damage.