To be perfectly honest, I think the whole "active mitigation" thing is a step in the wrong direction. I don't know of many people that thought the DK style of play was anything good, let alone people wanting that playstyle for all tanking classes.
I think Blizzard has a point. Threat being an actual challenge to achieve and maintain like it was in Vanilla made for boring, laborious tanking, and for ages now, the best tanks have been arguing that the responsibility of the tank is moreover than "to hold aggro," actually "to survive."
This is why we augment our gear for defensive stats and revile offensive stats (hit/exp becoming defensive stats in Mists). This is why our mechanics in raids are about minimizing damage we take, rotating cooldowns intelligently, and building your character around damage taken, whether it be by minimizing overall damage or spike damage.
The issue with less active mitigation, or basing the role of tanks around threat rather than defense, is that you end up with tanks who are little more than bad DPS. Our rotations exist to maximize damage we do. By moving toward a model in which the way we use all of our abilities, rather than just a 3 min and 1 min CD (or, for DKs, two 3 min and 12039810 1 min CDs) decides how well we survive, we are, for the first time, truly distinguished from DPS in gameplay, and that is as it should be.