Well in this thread you can make a deathwing fight and show the awesomeness! Here's my idea:
Part 1: Gunship Battle
In this instance you have just killed the previous bosses and are heading to Deathwings imba floating island on a gunship. On the way you fight black and twilight dragons. Then when you're nearly there a massive twilight dragon comes and is a mini boss. You just shoot at him, and some members of the raid can jump onto him and fight him shadow of the colossus style. Then he casts an ability called Fire Pulse, and everyone has about 10 seconds to get back on the ship or they die. He then turns all red and fiery and grabs your ship, before Alexstraza flys in, kills the dragon, and takes you on her back because your gunship is nearly destroyed.
Part 2: Floating Island
You land on a floating island in the sky, with an other island in the middle surrounded by lava where Deathwing is sitting. You speak to Alexstraza and she chats with Deathwing, then they wrestle in dragon form.
P1: While the two dragons fight, the lava moat around you bubbles up and drakonoids come out. Also, fire balls fly up out of it and fall down in the sky for you to dodge. After you've killed the first wave of drakonoids, half of the lava moat turns purple. Twilight drakanoids come out of the purple half, and black ones come out of the lava half. The group needs to split in two. One tank and the casters need to kill the twilight drakanoids, as they do an AoE for 100k damage often, so only a tank can survive and the healer couldn't heal lots of people for that much. The melees (and hunters) and another tank should take the Black Drakonoids, because they resist magic so casters won't work.
P2. A twilight and black dragon will come out each side and the same groups take them. The twilight dragon casts void zones and the black dragon crumbles the earth making the island smaller. Once they're dead an event happens where Deathwing gets Alexstraza weak and she lays on the floor in human form. Two twilight cultists come through a portal and drag her back through it. Then Thrall manages to get through the Twilight Portal and says he was held as a hostage but he's escaped. He then buffs the main tank to make him grow to the size of Deathwing.
P3. Then tank just tanks and dodges AoE. The two offtanks run around the islands and find twilight portals spawning then they get agro of the cultists who come out and find the next portal. When they get about 15 cultists on them they should run to the middle of the islands and let the casters AoE them and Deathwing at the same time. The casters fight Deathwing and AoE the cultists, and the melees need to attack Deathwing, but when he casts Wing Buffet you run away from the wings, when he Tail Swipes you run away from the tail and when he Flame Breaths you run from his head. You know he wing buffets after he Flame Breaths or Tail Swipes, so if he casts flame breath run to his tail and when he tail swipes you run too his head. At 75% the tank loses Thralls buff and shrinks, and Deathwing casts Death Eruption, and beakers and casters will need to jump off the island to mini islands in the lava river, the main tank, melee's and hunters need to run up Deathwings tail and climb on his back, and the offtanks need to do whatever's closer. After the 15sec cast the island erupts, everyone still on the island dies, the Twilight cultists die and the portal despawns. Thrall either sinks into the lava, gets thrown down into the sea, gets hurled into the sky in the distance or falls into a crack in the earth.
P3. Ysera and flys in with Malfurion on her back, and they fly in to heal the land. It becomes one big grassy island, and the lava river goes away. Ysera casts 'Anti Dragon' on Deathwing and he goes into human form. Deathwing gets furious, and sucks Ysera into a void zone and puts Malfurion in a portal to the Firelands, Abssysal Maw, Skywall or Deepholm, depending where he sent Thrall (into the Earth, Sea, Sky or Lava.) Now you fight Deathwing in human form, and a bar next to his nameplate. This shows when he's ready to go into dragon form again, and you must get him to 50% before it fills up or he crushes you all. You also need to avoid slow Water, Fire, Earth and Air elementals, and if they touch you you'll then get a debuff. Fire sets you on fire and you must get touched by a Water elemental to stop it, but the. You get the Water debuff, liquid form, where you become a water elemental and your group must dps you down to restore you. If you go to earth you get frozen as if you're in an ice block exept you can take damage. You're group must break the stone by getting you down to 50%. The air elementals will fling you round the room in the style of the belf boss in the nexus. Also, the ground will rumble often and spikes will shoot out, one shoting you, and Deathwing casts Meteor Strike, which strikes the tank for 75k and if he doesnt die from it a meteor targets a random person who glows red, and then it shoots down at them killing them and everyone near them. If you get him to 50% then you just survive until his power meter fills up and he can turn into his dragon form, then he shapeshifts and flees to the elemental plane where Thrall and Malfurion are.
Part 3: Elemental Plane (4 paths: Firelands, Skywall, Deepholm and Asyssal Maw)
Kalecgos comes in and makes you a port to the elemental plane. Each fight is different depending on where you go, and you kill a different leautentant of Deathwing there, all with different tacticts. Then you go to the chamber Malfurion and Thrall are, and they say Deathwing went to where Alexstraza and Ysera are. Then Thrall has a vision of them nearly dieng, and Chromie appears (Nozdormu can't really because of lore reasons, but if he is sorted out before then make it Nozdormu, not Chromie) and sends you back in time to when Deathwing arrived there. This place varies from fight to fight too, and it's either Blackrock Peak, Twilight Highlands or SW/Org (depending on your faction) which has been invaded.
Part 4 - Path 1: Blackrock Peak
P1: If the fights In Blackrock, you have to dodge fireballs Deathwing shoots at you and turn valves on rocks which shoot fire through a pipe. Then you keep doing this until you've done all the pipes
P2: then phase two starts, where you climb on him and unscrew his Elementuim Armour, then you kill tentacles which stick out of his bare skin. You do this ten times and he roars, you must hold on tight as he flys around, then you try and do more while he's moving, and occasionally he does a flip, which is when you need to grab on.
P3:When he gets to the Maelstrom you must rip off his last peice of armour, his chin armour, then he crashes down into the sea, you're falling but then green, blue, red and bronze drakes come and carry you back.
Part 4 - Path 2: Twilight Highlands
P1: In Twilight Highlands, you battle him in a phased version of the zone, with the same tactics as the original onyxia level 60 fight.
P2: Then he flys up, and you mount dragons, but don't worry, it's not like the Oculus, they just fly up and you use your abilities while mounted. If you're a tank you should use a red drake, because they'll stand still in frount of Deathwing. Melee's should use bronze drakes, as they curclenaround Deathwing and make sure you don't get agro, ranged should use blue drakes as they stay away from Deathwing but close enough to cast your spells and Healers should use green drakes because they go near to people with low health.
P3: It ends above the Maelstrom, and Deathwing falls into it.
Part 4 - Path 3: City Defence
P1: In the SW/Org fight, you defend the city with cannons, but then you go down on land and fight him in similar vehicles to the first Ulduar boss.
P2: Then you dismount and he casts flash teleport, and he teleports to UC/IF. Then you have to fight him with plague catapults for Horde and you need to kite him into the great forge in the alliance.
P3: Then he goes mad and casts again to TB/Darn. In TB you have to stop him destroying the city by summoning elementals to fight behind him, and in Darn you have to use those nelf catapult things which they use in the worgen starting zone.
P4:Then it's Exo/SMC, in Silvermoon you just fight in the dead scar while undead come out of the ground and attack you, in Exo you defend the front gate from Deathwing and shoot Outlandish lasers which come from spectral cannons which randomly spawn and you need to wuicly get to them before they despawn.
P5: Then it's the Maelstrom, where Deathwing dies in lore. You just jump from rock to rock until you find a glowing red rock, and if you're the one who finds it you press it and three more light up, you get three others to press them then four lasers fire at him and he dies.
Also, about it being too long and 'unfarmable'. Well, blizzard said they'll do more, shorted raids per tier in cata. So basically in this Deathwing instance, you walk into an awesome dragon lair, see Deathwing in the first boss room in human form, an ogre enters and says, "Lord Deathwing! Let me kill these intruders! It shall be my final test," and Deathwing says "You have failed me too many times in the past. If you are able to slay these rats, all your failures will be forgotten. But I can doubt you will. Go. Paint the lair with their blood." and that's the first boss.
The second one is after that, when Deathwing is talking to 5 dragons in humanoid form, Deathwing turns around and says, "Ahhh... That ogre failed me again. Not suprising really. He wasn't a good test. Before you face me, here is my true test! Time to face the Council of the Five Guardians!"
Then you go to the top of the lair Deathwing flys away, you chase him on your airship, kill the twilight dragon boss, then kill Deathwing who has the length of two or three bosses. 4 bosses overall, but this dungeon has the length of 7 bosses.
Also about how long it takes, if you wipe in the elemental plane part of the fight you don't start from the beginning, just the beginning of the elemental plane fight, and same with the twilight highlands, city or blackrock parts after, you start at the start of those if you wipe. Also, the fights in parts. There's the gunship ride to the island with the twilight dragons attacking you, then when it crashes at the end when Alexstraza comes you get permission to open the "Crate of Supplies" on the deck with loot in. Then once Deathwing goes to the elemental plane after the second part (the island fight) Kalecgos gives you rewards before he ports you over, and you'll have a time to rest and stuff before you ask him to port you over. There will also be loot given to you from the boss you kill in the elemental plane, and you'll have a break before you ask Chromie to take you to part 4, where you'll get more loot from Deathwing once you're done. So its not just one long boss, but basically 4 normal bosses.