My guild is working on Mount Hyjal now, taking advantage of the lifting of attunement. It's a fun instance, different from stuff before it because of the trash design. A little bit like Black Morass or the Eagle gauntlet in Zul'Aman.
Trash comes in waves on a timer, about 12 mobs per group. We have a paladin tank pick most of them up and hold them in place for AoE. Paladin tanks are magical hacks, they can hold aggro on an unlimited number of mobs and generate enough threat to outstrip the Mages and Warlocks AoE. Particularly against undead.
But it's bad to have too many mobs hitting the paladin, particularly the Abominations that do a knockback that makes him unable to use his shield. So my goal last night was to keep as many Abominations on me as possible. I did OK; in our WWS report I took just as much damage from Abominations as our paladin and about 20% more hits. Knockdown debuffs were about evenly split between me and the paladin, but I dodge so many I think I was doing my job. Still, I can definitely improve. It's like optimizing your damage meters, only this case what you care about is incoming damage.
Holding aggro against a paladin is not easy. At first I thought %26quot;AoE pull, spam Swipe%26quot;. But the paladin's handling the AoE aggro for you, really your goal is to single-target tank two or three Abominations to keep them on you and off the paladin. Once I figured that out your basic Growl / Mangle / Maul / Lacerate rotation worked well. The hardest problem was picking Abominations out of the crowd, lots of tabbing.
Hyjal's also a fun demonstration of druid versatility. For the first two bosses you want three or four tanks for the trash, but only one or two tanks for the boss. So I'd swap into cat gear and go DPS. The mobs are pretty squishy, too, so plenty of good melee damage. That's something I enjoy a lot about being a feral druid; being able to tank or DPS well in the same spec.
Update: went back to Hyjal the next week and improved my pickup of the Abominations. First week I was splitting Abominations about 50/50 with our paladin. This week was more like 60/40. WWS is a great tool for focussing and improving your gameplay. Turning on nameplates also helped (thanks, Karthis!).