Immerseus Guide Flex Mode - Siege of Orgrimmar Patch 5.4

Immerseus Flex Guide
This is a rather easy fight. Since its flex you dont need to have an exact comp, though something similar in ratio to 2 tanks, 3 healers and 5 dps should suffice.
Overview
Immersues has 2 phases. In the first he is there in the flesh and must be killed. The seconds phase starts when you kill the first phase. He will split into a bunch of adds that need to be healed/killed. I will now go into specifics. The bosses main mechanic is called corruption. This is tracked on his poiwerbar on your UI. The fight ends when his corruption hits 0. Corruption is removed in phase 2.
Phase 1
This is pretty much tank and spank, though you do have to be careful. DPS and healers will notice a lot of void zones. The raid must be seperate from the tank as the boss does a damaging frontal cone. Players can spread out in this phase if they want, however its only really important to spread fully around the room in the next phase.
First lets talk about tanking. His tank swap ability is called Corrosive Blast. This does about 600k damage and casuses damage taken by corrosive blast to be increased by 300% for 45 seconds. This ability is a frontal cone, so other players (and the off tank) must not stand in front of it. Once the first tank is hit simply swap.
They are caused by sha bolt with does 15k damage and then puts a void zone on the floor that does 50k damage per second.
He also does an ability called Swirl which makes some moving void zones and a large wave of water that moves around the room. The wave can be avoided with personal speed cooldowns, but as you can see in the video I fail this and the reprocussions are next to nothing. The tank needs to be in melee range at the end of swirl.
Seeping Sha isnt a problem. If you run inside the boss you will get knocked back and have 100k damage dealt to you.

Phase 2
This is the add phase that will lead to reducing the bosses corruption level. The adds will spawn at the outside of the room and will move towards the middle. Once they hit the middle the raid will take damage, so be sure to kill/heal as many as possible. The raid needs to be spread throuought the full 360 degrees of the room to get coverage.There are 2 kinds of adds:
Friendly - These must be healed up by healers. Its likely you wont be able to get all in your area, thats fine just do what you can to heal up as many as possible. As an add gets healed its movement speed decreases. Standing near one when its fully healed gives a healing done and mana regen bonus
Hostile: These are very easy in flex. Simply kill them. Standing near one when it does does a bit of damage and increases your damage done. These adds can be snared etc so be sure to do that as you will get more dps time on them. Not much is gained from explaning the numbers, but as the fight goes on there will be relitivly more healing adds spawned in comparison to dps adds. In our group this was a little problematic as the healers were not that great at dealing with them.
After the adds reach the centre of the room immerseus will reform, taking the fight back to phase 1. Subsequent phase 1s will have less health.