I don't think this even needs to be said, but huge huge spoilers ahoy.
With patch 5.4 going on the PTR with the quickness, we're starting to see just who, exactly, we're going to be fighting in the Siege of Orgrimmar raid, and it's definitely not as straightforward as we might have thought. With the folks at Wowhead having the zone page and Dungeon Journal information up, we can take a look at what's to come. Be warned, there are spoilers for the upcoming raid in plenty past this link. If you don't want to know what the bosses will be in this raid, then do not read past this point.
Okay, now that they're gone, let's gorge on what we can discover.
First off, the Siege doesn't actually begin in Orgrimmar. Looking at the zone page, we see the following bosses:
- Immerseus: Tears of the Vale
- The Fallen Protectors
- The Sha of Pride
Following that, we seem to be on track to head into Orgrimmar itself, as seen in the following list of bosses. Only a few of them have journal entries, which we'll link to and discuss again after the link.
- Galakras: Zaela's Drake
- Iron Juggernaut
- Kor'kron Dark Shaman: Haromm and Kardris trained thousands of shaman to whisper reverently to the elements to requisition their aid. The army of Garrosh, however, does not ask -- they take what they desire in the name of the True Horde. Dark Shamanism forces the elements into servitude, twisting them into burned-out ash, corrupted waters, and toxic air.
- General Nazgrim: Once a grunt in service of the former warchief, Thrall, General Nazgrim rose quickly through the ranks after overwhelming victories in Grizzly Hills and the sunken city of Vashj'ir. Fiercly loyal to the Horde and bound by a rigorous code of honor and duty, Nazgrim will hold the line for his warchief until his dying breath.
- Spoils of Pandaria
- Thok the Bloodthirsty
- Siegecrafter Blackfuse
- Paragons of the Klaxxi
- Garrosh Hellscream: Warchief of the True Horde
The big news is the four phase Garrosh fight. It definitely seems as though Garrosh is the one in control, and not Y'Shaarj controlling him: while it's clear that Garrosh is empowering his soldiers with the essence of the Old God, the fight (based on the journal entry) seems to be more Garrosh using Y'Shaarj as a weapon and power source and less about being driven mad or corrupted by his power. Whether or not it ends up that way we'll have to wait and see.