Various sites have essentially the same bullet points
This is something new to WoW as a raid that is a completely new experience for each faction!
The Alliance will land at the docks and work their way up the pyramid (and seeing new locations inside) and work their way up to Rastakhan.
Horde will start North of the pyramid and work their way to Rastakhan (which is the midpoint of the raid). Then you'll work your way to the docks and fight against Alliance commanders including Jaina on the high seas!
Once your raid is complete, you can talk to your scouts to get information on the other factions movements which allows you to fight the other 3 unique bosses that you haven't fought yet.
1) Please note that they carefully said that you are fighting TO Rastakhan, with no inkling of how it will go. I would daresay that ''OH NOES, HE TURN BAD'' is a distinct possibility, considering that this is a rather common career choice for monarch on Azeroth. Also, if Troll Emperor is the midpoint of the raid for both factions what could be the equivalent for the Horde as a mid boss ? Could this be that both factions fight Rastakhan ? With a troll princess having a very tough choice that is oddly common amongst WoW characters ?
(My pet hypothesis is that, that's convenient, Troll Emperor have made a pact with a Graveyard Spirit. Conveniently, he can be killed by faction A and get rezed-turned evil to face faction B. That or Baron Samedi)
2)The structure indicates a sequential raid (Alliance first attack THEN you fight your way through the docks to pyramid, climb pyramid, chat with him….Here, I would point that there are some difference between sites. Some report ''through the Alliance'', some omit that point. Would this means, gasp, fighting trolls through a trollopolis ? Never occurred at, say, Zul Farak, Zul Gurub, Zul Aman, Zul Drak…)
3)What puzzle me is how you can have nine bosses including three unique ones in an instance where there will be likely a non Shrodinger canon (IE, both storylines will be true, not just yours) Hypothesis….
A)Blizzard goes cheap, Coliseum size, and you fight on each side 3 captains that will be mirrored the other side (up the pyramid for the alliance, down the pyramid for the Horde)
B)Blizzard goes creative and each faction have a rare ''lose'' raid encounter-IE, they have to hold the line against the enemy for a given time, which is mirrored by an opposite encounter breaching a defence line. Both can be true.
C)The final boss and it's mythic only counterpart are usually the most important lore part. Now, we can imagine a gunship icecrown 2.0 scenario of course. But what if the final boss is the same for both factions. What kind of encounter with a common foe could there be on high seas ?