I tried smite spec this week, and I did warmaster just fine. We put all the melee in one group and all the ranged into another group. My smite spam would heal melee and I would just PoH for the ranged. When the big aoe hit I would pop AA and PoH spam the ranged up. We talked ahead of time so I healed group 2 and the Hpally heale group 1 so we didnt overheal.
I have been talking to a lot of different 8/8 heroic priests lately, and all say don't even do disc at all unless you are tank healing SoS / ToT in 25m, otherwise just go holy. I don't know why, WoL disc ranks just as high if not higher then holy on almost every fight even on 10m.