At this point mastery is the king of survivability stats if you are dieng constantly and haste takes a close back seat.[COLOR="red"]
Haste reduces the damage the best between the big hits and make the time outside the big hits less threatening.
Stamina is only better when the damage you take outside the big hits and when your SotR is down is actually dangerous. A.k.a. when you can die on the bosses "low damage" part. This usually happens more in 25 man because boss melees harder in 25 man, this is partially why 25's want more stamina than 10's usually, and why stamina is actually kinda bad in 10 in comparison to haste and mastery.
Not to mention the added dps from haste.
Edit: Just as an example. If you are at say 50% SotR. Which is kinda standard. As long as you have more than 450k health, mastery is better than stamina for reducing the high damage abilities per point at gem exchange rates. 1:0.75