OP you are right with regards to paladin/warrior mastery and stats, they shouldn't stack stamina atleast not until they hit the 102.4% unhittable mitigation mark.
But for DK's and I believe a slightly lesser extent Druid Tanks, Stamina is still our best stat due to the increased self healing, the increased blood shield, the increased vengeance etc etc, until that changes no DK atleast should stack anything but.