At the start of the encounter, the group will want to kill off three of the four corruption tentacles, with the tanks temporarily holding onto the three hideous Amalgamations that spawn as a reaction to that.
Once they’re out, the group should intiate a Deathwing barrel roll by stacking up on one side of his back on one of the open wounds to make sure that they don’t fall. Once the roll is finished and all of the extra adds have fallen off, everyone should focus their attention on the remaining tentacle and burn it down, spawning a last Amalgamation which must be tanked.
For efficiency, you’ll want to tank it by one of the armored plates. Once that’s in place, make sure that you have a good threat lead on the large add and do what you can to bring the many smaller Blood adds to you where you’re tanking, be it by taunting them whenever you can or using some of your ranged abilities to get their attention. It will primarily be the DPS’s job to burn them down to just pay attention to their location in case they die a bit too far away and you have to shift over to absorb them into the large add.
From a tanking perspective, the fight isn’t that complex. You just need to hang onto the Amalgamation and be sure to get ready to book it onec it’s absorbed 9 of the Bloods and is getting ready to blow.
Keep a close eye on the health of the thing when it’s fully grown and move away from it as soon as possible when it starts to cast its explosion.
Blowing up an Amalgamation next to an armored plate will blow off the armor and reveal a Tendon that holds it in place temporarily. The DPS requirements on these tendons are fairly high so be sure to do what you can to assist in their demise, be it with your own small contribution to damage or saving certain abilities like Shattering Throw for when you know they’ll be ready to be burned down.
Once the tendon is killed, the armor will fall off permanently and the fight will essentially reset, spawning four more Corruption tentacles and restarting the entire process.
So essentially, once you get down the first Amalgamation, that’s pretty much the sequence for the rest of the fight and it’ll just come down to a matter of getting everyone to hold it together and repeat the procedure enough times to land the kill.
Best of luck on your dragon ride!