I like druid for my tank (have also tried DK) because I can duel spec it to boomkin for raiding (boomkin, 3x mage, ele shama in raid/feral druid, 3x mage, resto sham otherwise). Also has a few good emergency buttons, mark of the wild and spammable aoe threat. Shadowmeld can save a wipe if something gets away and kills your healer. Druids suck for pvp though.