Much like Commander Shepard and the Reapers, we've known for a long time that doom was coming for us block tanks, some way, some how. The stack has been on the nerf list for quite some time. We dodged the bullet in 4.2, and then in 4.3, the devs called off the dogs entirely, giving us a respite. However, with the recent publishing of Ghostcrawler's Mists stat changes Dev Watercooler, we now have an idea how our most favorite stat is going to be unceremoniously slice and diced.
The changes to block will have far-reaching consequences for our class (as well as protection warriors). Obviously, this is pre-alpha and thus a nerf only in theory, but it's obvious what the intent is here: the defenestration of block to prevent mastery from being the powerhouse stat and block from being the powerhouse mechanic that both were for much of the Cataclysm cycle. And while it's evident that something needed to be done to block in the long run, I'm not quite sure that the changes Ghostcrawler outlined were the best avenue to take.