Il'gynoth, Corruption Reborn
This fight has two phases which repeat. After Il'gynoth is defeated his Organs are exposed and you enter Phase 2. Once an Organ has been killed you return to Phase 1 and all other Organs return to full health, however Blood of Ny'alotha now spawn from this location. As the fight goes on more and more Bloods will spawn.
Phase 1 (Il'gynoth)
Eye of N'Zoth - This is the tank swap for this encounter. Il'gynoth will cast an eye beam towards the active tank, dealing a large amount of Shadow damage. The tank will then receive a debuff increasing damage taken from Eye of N'Zoth by 75%.
[Heroic] Touch of the Corruptor - Several players will become mind controlled for 1 minute. If these players melee anybody they will also become mind controlled. To break this mind control you need to reduce their health to 30%.
Note: Removing it via an immunity will still trigger Cursebreak. You are able to pre-immune it.
When you enter Phase 2 a new add will spawn called Clotted Corruption. This add is tankable.
Absorbing Charge - This is a 2 second cast where the add will charge in a straight line and deal large Physical damage to anyone hit. If any Blood of Ny'alotha are in the path it will absorb them gaining Reconstituted Blood which grants 10% damage for each Blood absorbed.
Tank Damage Profile
Face the boss away from the raid when you are tanking so Eye of N'Zoth does not hit other players
Swap on 2 stacks of Eye of N'Zoth
During the intermission keep the Organs interrupted to ensure additional Bloods don't spawn
[Pending Final Trinket Tuning] Lingering Psychic Shell can be very useful for taking hits from Eye of N'Zoth as when it is activated the entirety of the hit(s) will be mitigated, rather than just the absorbed amount (as of the most recent tests on PTR)
Vengeance Demon Hunter
Sigil of Chains can be useful later in the fight to group a lot of Bloods of Ny'alotha together
Ursol's Vortex can be useful later in the fight to group a lot of Bloods of Ny'alotha together
You can Mass Entangle the Bloods of Ny'alotha to allow them to group up for more efficient cleave
[Heroic] Typhoon can be useful to keep the players mind controlled with Touch of the Corruptor away
Blood Death Knight
Gorefriend's Grasp can be useful later in the fight to group a lot of Bloods of Ny'alotha together