Bastion of Twilight: Cho'gall

The last normal mode boss of Bastion of Twilight is a complicated fight with an interesting mechanic called Corrupted Blood, more on that later.

Similar to a lot of Cata raid bosses has Phase 1 from 100-25% life and a burn Phase 2 from 25-0%.

Phase 1 Abiliites:
Conversion: Random target starts channeling Worshipping spell. This causes Cho'gall to gain stackingTwisted Devotion every 3 seconds. Should be Interrupted.
Twisted Devotion: Stacking buff increasing Cho'galls damage by 10% for 20sec.
Flame's Orders: Cho'gall gains 20000 fire damage with each melee swing and patdches of fire spawn.
Shadow's Orders: Cho'galls attacks cause Raidwide AOE shadow damage.
Fury of Cho'gall: Cast on tank. Inflicts 30,000 Shadow and 30,000 Physical damage and increases damage taken by Physical and Shadow by 20% each. Lasts 45 seconds.
Summon Corrupting Adherent: Cho'gall summons a Corrupted Adherent with 1.7 million HP (10-man)/4.98 million HP (25-man) from the nearby portals.
Fester Blood: This will spawns five Congealed Blood of the Old God with 75,000/300,000 HP each from each dead Corrupting Adherent's blood pool. Living Corrupting Adherents will gain a raid wiping shadow AoE if they are not killed before this is cast (approxiamtely 30 seconds).

Corrupting Adherents:
Depravity: Inflicts 21937 to 23062 Shadow damage to enemies within 50,000 yards and causes Corruption. Interruptable. 1.5 second cast
Corrupting Crash: Fires a shadow missile at a target, dealing 43875 to 46125 Shadow damage to all enemies near the impact. Targets hit by the Corrupting Crash have corruption applied to them.
Spilled Blood of the Old God: On death: The slain Adherent to the old god spills its corrupted blood. Inflicts 14625 to 15375 Shadow damage to enemies within 0 yards and applies Corrupted Blood. Leaves a large pool of blood that persists and applies corruption to anyone standing in it.
If not killed before Cho'gall casts Festering Blood they gain:
Festering Blood: Inflicts 43875 to 46125 Shadow damage every 2 sec and causes Corrupted Blood. Raid Wipe

Congealed Blood of the Old God:
Untankable ooze creature. Causes Corruption when they melee swing. Can be snared and rooted.

Phase 2 Abilities:
Fury of Cho'gall: Cast on tank. Inflicts 30,000 Shadow and 30,000 Physical damage and increases damage taken by Physical and Shadow by 20% each. Lasts 45 seconds.
Corruption of the Old God:Cho'gall becomes completely corrupted by the Old Gods, inflicting 4875 to 5125 Shadow damage every 2 sec to everyone in the room.
Darkened Creations: Cho'gall summons 4 (10) 10(25) Darkened Creations with 166,000 HP. Tentacles!!!

Darkened Creation
Debilitating Beam: Reduces healing and damage done by 75%. Inflicts 4875 to 5125 Shadow damage every 1 sec. Causes Corrupted Blood every 1 sec. Lasts 10 seconds. Interuptable but undispellable.

As if this fight is not complicated enough there is another mechanic to remember. Being hit by abilites you should be avoiding will apply a stacking Corrupted Blood debuff. These abilities are:
Dark Sickness - 5
Accelerated Corruption - 2 per second
Sprayed Corruption - 5 per 2 seconds.
Spilled Blood of the Old God - +5 per second of standing in it.
Congealed Blood of the Old God melee - 2 per hit.
Corrupting Crash - 10
Depravity - 10
Festering Blood - 5
Debilitating Beam - 2 per second.
Corruption of the Old God - 1 per tick

As you gain stacks of Corrupted Blood you become more and more powerful. Eventually destroying Deathwing in one mighty blow and replacing him on everyone's loggin screen. No, you gain these nasty debuffs:
Corrupted Blood: Your blood is corrupted! Increases damage taken from Corruption of the Old God by 2%.
Dark Sickness: You vomit inflicting 39000 to 41000 Shadow damage to friends in a 5 yard cone in front of you, also causing Corrupted Blood. Unsure when this triggers.
Accelerated Corruption: Your Corrupted Blood has gone to your heart and it is accelerating! You are becoming more corrupt by the second! Causes two stacks of Corrupted Blood per second for one minute. Gained at 50% corruption. (Probably is dispellable)
Absolute Corruption: You become a Faceless one. You receive 100% less from healing but inflict 100% additional damage and spells are cast instantly. Unsure if you are mind controlled or if you are just uber powerful until you very quickly die. I'm guessing your mind controlled.

Tactics:
Tank swaps on Cho'gall when he does Fury of Cho'gall.
Damage will alternate between heavy tank (Flame's Orders) and heavy raid (Shadow's Orders).
Corrupting Adherants are off tanked. They need to die in a corner before Cho'gall casts Fester Blood. Their pool of congealed blood is quite large and we do not want the Congealed Blood of the Old God (oozes) spawning too near the healers/ranged.
When the oozes spawn they need to be quickly killed by ranged before they hit anyone.
If people fail on avoidable damage they will start gaining Corrupted Blood. This means during the burn phase from 25% to 0% you are taking more damage from Corruption of the Old Cold and the raid will die quickly. The second phase is when we use all cooldowns etc.
In phase 2 it seems the raid can safely stack up on the boss and use AOE healing to get through the corruption of the old god for as long as possible. DPS will probably need to switch to the tentacles as they spawn and someone needs to interrupt the Debilitating Beam.