The big, enraged/mutant adds was our downfall last night. Its definitely a challenging tanking assignment but our biggest problem came when the empowered mobs would stack up on one side (usually the side opposite where I was) and start taking people out.
As a warrior, the hardest thing for me was gathering the three adds as they spawn. It worked really well having a DPS DK drop D&D on the third spawn point while I stradled the other two and picking them all up there, peeling the 3rd off the DK. From that point, shockwave is your friend. Spell reflect is helpful too. I'm considering going back to imp but with all those mobs and trying to hold aggro, threat is at a premium.
We never made it to phase 2 but we got some reps in on it.
The High priest trash as was mentioned above wiped us the first time. We figured out the gimmick and then annihilated them from then on. Just have the person with the debuff run away from the raid.
your hat may be nice, but I have the little white tank top that says Legendary right across my boobs. I win. (or more correctly, H wins)