Tank switching, Death Knight trick
Just killed this last night, we found a handy trick with Death Knight tanks that allows you to not have a tank ported down. Anti-Magic Shell will prevent application of the Twilight Shift debuff, if timed properly this will let the 2nd tank run out his debuff safely and take the dragon back without having to shift down into the Twilight Realm. This combined with a Subtlety Rogue means that you can keep 9 people up top for the entire fight, worked fantastic on our kill last night.