Abilities:

Corrupted Blood Mechanics:

• Corrupted Blood - Increases damage taken from Corruption of the Old Gods by 2%, stacks to 100
• Corruption: Accelerated - Causes 2 stacks of Corrupted Blood per second for 1 minute, gained at 25% corruption, magic dispellable
• Corruption: Sickness - Causes you to vomit and inflict 40K shadow damage to allies in a 5 yard frontal cone also causing corruption for them, occurs at 50% corruption
• Corruption: Malformation - A malformation grows out of your back shooting shadowbolts at nearby players, occurs at 75% corruption
• Corruption: Abosolute - At 100%, you transform into a faceless one, recieve 100% less healing, but gain 100% more damage and all spell casts become instant.

Corrupted Blood Gains:

• Dark Sickness - 5
• Accelerated Corruption - 2 per second
• Sprayed Corruption - 5 per 2 second
• Spilled Blood of the Old God - 5 per second
• Congealed Blood of the Old God - 2 per hit
• Corrupting Crash - 10
• Depravity - 10
• Festering Blood - 5
• Debilitating Beam - 2 per second
• Corruption of the Old God - 1 per tick

Phase 1 (100-25%)

• Conversion - Causes target to channel Worshipping spell on him gaining Twisted Devotion stacks every 3 seconds, Worshipping is interruptable
• Twisted Devotion - Increases damage done by 10% for 20 seconds
• Flame's Orders - Adds 20K fire damage to each melee swing and spawns fire patches
• Shadow's Orders - Adds shadow damage aoe to each melee swing
• Fury of Cho'gall - Blasts primary target for 30K shadow and 30K physical damage and increases damage taken by shadow and physical by 20% for 45 seconds
• Summon Corrupting Adherant - Summons adds
• Fester Blood - Spawns 5 Congealed Blood of the Old God from each dead Corrupting Adherant, and causes Corrupting Adherants to gain a massive raid wiping AoE, casts about 30 seconds after summoned

Corrupting Adherant (1.7M / 4.98M HP)

• Depravity - Inflicts 22K shadow damage to enemies within 50K yards and applies Corrupted Blood, 1.5 cast, interuptable
• Sprayed Corruption - Inflicts 35K shadow damage in frontal cone and applies Corrupted Blood
• Corrupting Crash - Fires shadow missile at target dealing 45K shadow damage to all enemies near impact, applies Corrupted Blood
• Spilled Blood of the Old God - When killed, leaves puddle that inflicts 15K shadow damage  to all that stand in them and applies Corrupted Blood
• Festering Blood - If Fester Blood buffs them, inflicts 45K shadow damage every 2 seconds and applies Corrupted Blood

Congealed Blood of the Old God (75K / 300K HP)

• Untankable
• Snared and Rootable
• Applies Corrupted Blood per melee hit

Phase 2 (25% - 0%):

• Fury of Cho'gall - Same as above
• Corruption of the Old God - Inflicts 5K shadow damage every 2 seconds to everyone in the room
• Darkened Creations - Summons 4 of them

Darkened Creations (166K HP)

• Debilitating Beam - Target reduces healing and damage done by 75%, inflicts 5K shadow damage per second gaining Corrupted Blood, lasted 10 seconds, not dispellable.

Notes:

• Pay attention to your insanity, um corruption
• Note the different states of it
• Magic dispel ASAP at 25% (or you corrupt faster)
• GTFO away from people at 50%  (or you vomit on them)
• GTFO away from people at 25%  (or you aoe shadowbolt them)
• Though at 100% you have one last hurrah at massive DPS before you die

Phase 1:

• Interrupt the worshipping
• Don't stand in fire
• Adherants are Faceless one that are summoned
• They do shadow crashes and frontal cone damage that's interruptable
• Let ranged finish them off as they also leave a void zone on death
• Fester Blood is cast 30 seconds after Adherant
• If alive, Adherant gains massive shadow aoe likely raid wiper
• If dead, spawns 5 oozes that you have to kite around (and kill), if hit, you get corrupted
• Fury of Cho'gall, that sounds like it might neccessitate tank swaps

Phase 2:

• Shadow damage aura now which also corrupts your blood
• Tentacles spawn that shoot beams at you which lowers your damage and healing, and corrupts your blood, kill those
• Basically seems like dps burn time before you're all corrupted