I have just started to discover the fun that is being the ironman disc priest
Reflective shield
Pain suppression
Focused will
Blessed recovery

Take a holy priest into the arena and watch him get rolled in 20 seconds by a spamstring warrior or lolstep rogue. Take a disc one and they can beat on you while you go have your taxes done, watch a movie, and then maybe you may have to hot yourself.

A disc priest+ shammy boxer= one pissed off team that just got rolled