If Lady isn't tauntable, the only way I can think of it working is that, you have 2 tanks that build aggro constantly and have rogues and hunters MD to them. Tanks switch naturally when ones aggro falls enough. Problem is, the DPS have to be really careful with the aggro they generate to not overtake the tanks.
Also, if adds continue to spawn you probably need 4 tanks. Sounds interesting.
Anyway, if these reports are accurate, I'm disappointed with the hard modes, I was vast enhancement of tactics, and perhaps even have a couple more phases per boss on certain encounters.