"Who tanks now," you ask? The same folks who always have: the good tanks.
The majority of each class's playerbase always bitches about being overnerfed all the time compared to all the other classes and blah blah blah. And then there are the players who get shit done regardless. ;p
Of the classes I've played, the only one that felt like it took way too hard a hit from the nerf bat was Warlocks in the transition from BC to LK, when affliction and destruction (specifically the wrecking ball that was 0/21/40) got completely beaten to shit. Pretty much stopped playing it after that - not that the class was unplayable, I just didn't like the new "style" of warlock with the bouncing Haunt dot-tide shenanigans or the chaos-fire silliness in deep destro, and I've never liked relying on a pet so Demo was never appealing. That was one nerf I could see as the cause for justified WTF's on the part of the playerbase. Most of the tears are shed over a few number changes here and there, though, which strikes me as silly. There's a difference between making something weaker and completely removing abilities (siphon life, demo-sac-destro bolts, etc.) from the game. The former is just something you adapt to; the latter tends to dramatically change how a class plays, which is sort of a big deal.