In my mind i see the SOO playing out like :
2 slightly different raids depending on which faction you are.
Horde :
You start off in the echo isles, with all the horde leaders detailing the attack plans, after a short run you plus Vol’jin encounter a huge 3 way battle between Garrosh's loyalist forces, the Alliance and the Exile horde member/races in Razor Hill. Razor hill at this point has become a huge military base with zeppelin docks and a port. The alliance has landed ships on the coast and the loyalists are having a huge naval battle. After a set amount of mobs has been cleared the first Boss appears in Razor hill.
Short Rp scene with vol’jin and the raid clears some more mobs and then steals a Zeppelin to avoid the massive army garrosh has marching to Razor Hill. Flying low so the raid can see/avoid the massive battle below, you get attacked by an alliance airship and a loyalist zeppelin (one on the left one on the right), both ships have mini bosses that need to go down before garrosh and a squad of kor'kron elites attacks the zeppelin. this will be a race to kill the captains of both the airship and the zeppelin while a part of the raid attempts to hold garrosh off (fight plays like Morchok,) half the raid takes garrosh, killing the kor'kron before they overwhelm the tank and the other kills the captains then hits a button to set that ship to self destruct.
Zeppelin crashes into Org front Gate, The raid reforms and finds garrosh body missing. Org is now flooded with Dark shamans summoning powerful elementals. The raid attempts to kill them before the ritual completes but fails. The next raid boss is corrupted elemental lord created by the shamans using parts of rag and al'akir.
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The Alliance starts in Ashenvale fighting Gorrosh’s loyalists on the border of Azshara, a Massive night elf army reinforced with tanks and airships attempt to push past the blockade. The first boss appears on the bridge connecting to 2 zones after a set amount of mobs has been cleared. This boss has the same abilities/HP/Tactics as the Horde side first boss
After the fight the loyalists sets off a bomb blowing up the bridge, separating most of the alliance army from the raid. The raid lead by glen graymane rides south taking out small groups of guards on the way to the back gate. The mining pits has been converted into a tank depot, The raid steal a open top convey and get in the crossfire of an Horde rebel tank and a loyalist warmachine (one on the left one on the right), both vehicles have mini bosses that need to go down before garrosh and a squad of kor'kron elites attacks the convoy.
This will be a race to kill the captains of both the tank and the warmachine while a part of the raid attempts to hold garrosh off (fight plays like Morchok,) half the raid takes garrosh, killing the kor'kron before they overwhelm the tank and the other kills the captains then hits a button to set that vehicle to self destruct.
The Tanks crashes into Org’s Back Gate, The raid reforms and finds garrosh body missing. Org is now flooded with Dark shamans summoning powerful elementals. The raid attempts to kill them before the ritual completes but fails. The next raid boss is corrupted elemental lord created by the shamans using parts of rag and al'akir.
--------------At this point the horde/alliance raid follows the same path----------
After killing the boss the raid can go 1 of 3 ways, All three must be cleared in order to unlock the last wing (Like ICC).
Path 1 : Into the Drag, players disarmed Bombs garrosh has planted in the city just incase the alliance / horde gets into his domain. The Boss is a group of mercenaries called "DarkWaters INC".
Path 2 : Onto the Cliffs, Player take the lifts up to the cliff face in order to take out the AA guns, Mages, Shamans and wyvern raining death on the NPC's below. The boss here is a wyvern broodmother mutated by Garrosh’s experiments..
Path 3 : Goblin Slums, Garrosh plans to flood the city in an attempt to kill the invaders using his shamans. Last Boss is a Former Twilight hammer ascendance shaman, The Tidebreaker.
Players then head to the Cleft of Shadow, here is little trash. The next boss, 2 Dire Orcs are connected by a beam (if one dies before the other, the other enrages and gains new abilities). The bosses damage changes depending on the distance between the 2. Some abilities do more/less damage, others gain an extra effect.
Into The Caverns:
Trash :Waves of Flame Hounds and Shamans until you reach the center of RFC. You hear Garrosh Screaming at something. A dark shaman enters and summons garrosh’s ultimate Weapon. Using what he saw in northrend, the events of the Cataclysm, and the power the dark shamans, Garrosh has reanimated a Dead Sha and empowered it. Now he turns it loose on you.
With the Abomination Dead, The raid heads off to take garrosh on.
Garrosh, with the bell is giving a speech to the Black prince about power and control. Players then engage him in a epic 5 phase fight. Garrosh slowly lets the final sha take control in an attempt to win the fight.
With the leaders of both factions present, The High king demands that thrall disband the horde or Org will be razed. The black prince freezes the leaders in place stating that he needs both factions ready and able to take on the next opponents.
“One of you will fall, but not this day. I still need you”.
He then teleports all alliance members to stormwind.
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I understand that with different bosses, the race to worlds first will become an issue (some will say the bosses on one side is easier that thiers) however i feel this will fit theme of the expansion.