With the Throne of Thunder echoing in the distance, it will not be much longer before tier 14 is a fading and pleasant memory for many raiders. I think it's a fair assessment to say that this tier has been one of the most successful in WoW's history, at least from an encounter design perspective. An unexpected follow-up from the doldrums of Dragon Soul, the raids of Mogu'shan Vaults, Heart of Fear, and Terrace of Endless Spring have been interesting and (most importantly!) engaging -- especially for tanks.
Remember that in the closing days of Dragon Soul and Cataclysm, there was a general feeling of ennui in the raid tanking community. Between the nullification of threat, the introduction of Vengeance, and the seeming dumbing-down of raid mechanics throughout Cataclysm, the sentiment was that Blizzard had given up on making tanking interesting at anything but the heroic raid level. And even then, by "interesting" it meant you would have to cope with much, much more damage. Obviously, it's human nature to assume that past is prologue and as such many tanks assumed the worst was yet to come.
So imagine the surprise when the mists dispersed and the land of Pandaria revealed an unexpected renaissance for raid tanks.