With T15 4p: Haste(4500)>Mastery+1>Haste
Without 4p: Haste(6500)>Mastery+1>Haste
I was running ~6500 before the T15 4p so going to assume that is where I will be comfortable again but hard to say since I'll be running with so much more mastery boosting viable PB events.
Looking at a 7 kill night I was proc'ing Purifier once very 51 seconds on average. +1 Chi/min = ~2500 haste if I remember right so adding about 2k to my current rating should more or less compensate for the 4p loss.
Will be using RoRo w/ Mastery+Crit balanced but could go all out mastery for another +5% but I think I'm good since I'm also switching to the tank meta/cloak. So this is current setup:
http://www.askmrrobot.com/wow/gear/usa/stormrage/rikimu