I prefer tanking the way it is now. Mastery added a lot of value to it. I sure as hell don't miss the old Tri spec I had to get for S3D.
The decision to make one spec the dedicated tanking spec was also the best they ever made concerning DKs. It was horrible to see talents and abilities getting buffed and nerfed in major ways with every patch because each spec had to be able to tank/dps/pvp-
There are only two things I really miss: Raising and Ally as a Ghoul and Shadow of Death. But I can see why both were removed.