Currently, Alleraz, yes our mitigation got nerfed a bit, not 'hard', by any means, but Guardian mitigation was just stupid to begin with, so, for me, the nerf is almost unnoticible.
Guardian Druid has always been probably the easiest to learn and perform ADEQUATELY, But a skilled, top performing Bear simply can't be beat, especially on heavy add fights. I recently (WoD) began playing a Blood DK, and they are ALOT of fun, time will tell if I can perform as well with this Spec as I do with my Bear. I will say this, I have Main'ed a Bear since late Wrath, and, played Well, Bears have ALWAYS been one of Best Tanks, in terms of survivability AND dps.