Originally Posted by
Pasture
I think it depends on what you're playing with. We don't have a disc priest in our guild and mastery fills in a niche that none of the other healers can.
Either way I don't think it's appropriate to refer to mastery as situational. On the majority of fights it will account for 20+% healing. There are very few fights for which mastery is a bad stat.
Either way, haste vs mastery has been around for a while. In Cata haste had it for me. In MoP it's all about the mastery. With a 4 second HS and EF on the raid we're pretty effective at reacting without the additional haste, and big tank / raid damage can be anticipated and pre-cast.