It looks as though Haste may be stronger than Mastery for MoP. As ret, we no longer have reliable fillers between cooldowns, so having CS, Judge, and Exo coming up very frequently seems more important than bonus damage. I have tried out both and when stacking mastery I find myself sitting there doing nothing for a LONG time because CD's are so long. Haste is amazing. My holy power builders are almost always up, never waiting for them and if I am I have Holy Prism as a filler on a 20 sec CD. I am a multi top 100 world parsing ret pally in 4.3. I am still theory crafting, but comment on what you think about mastery vs. Haste as ret.