Stealthed through it on the PTR on a friends Druid, thought I would post some of the pictures-
wanted to add a few pics...here's what stealth can get you:
Hydross up close and personal:
After sneaking through ~3 large groups of mobs I came across The Lurker:
These Locked Serpentshrine Consoles appeared by every boss, probably unlocking with that bosses death, and eventually unlocking Vashj's chamber.
After moving to the NW of that picture (it's sort of like a loop, you can choose to go Leo->FLK->Morogrim or Morogrim->FLK->Leo but the 1st choice was blocked by mobs and I couldn't get through.) This of a picture looking away from the hallway to Morogrim, back towards the entrance.
There's a murloc(RWWRARARGGRALL) pat you can see in the bottom of this picture. The big show is the fatass behind them, in a room that was filled with the same murloc pats.
In the next room was Fathom Lord Karathress, surrounded by Underbog Colossus pats and his adds. A close side-view:
And a farther back front view:
The next hallway had ~2 pats and then a very large room with this guy:
Leotheras The Blind's room had quite a lot of trash, but not as much as the main circle around Lurker.
And a back view of his demon form, as well as some of the trash: