Finally hit 90 on my DK last night! Also got Dynamic Duo as a result.
Then I managed to pick up a number of Dungeon Achievements:
Hydrophobia: Majorly surprised I got this one. Never could do it quite right on my Hunter.
Burning Man: Pretty easy, just lead the boss to the Target Dummies and let him do his little flaming fists.
And Stay Dead!: This one I thought was gonna go horribly wrong, but I managed to freeze half of 'em with Remorseless Winter and then we AoE'd the hell outta them. Had to Brez somebody during that mess, but we ended up ok.
Keep Rollin' Rollin' Rollin': Hit boss with about 20 barrels and kill him.
Hopacalypse Now!: Tricky since it's hard to tell if you've got 100 up. Killed our Tank eventually, but we managed to get him back up and grab the achievement.
Ling-Ting's Herbal Journey: I couldn't find any, but everyone else did and we all got it. Also gives you a Hopling pet.
Feels good man.