Anyway.. I've looked up some video's of Immerseus fight in heroic mode.
Hope you find it helpful.
Warcraft Academy (25man hc)
Fatboss (10man hc)
Here is a link to icy-veins that has some detailed information on the boss and the fight.
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Differences From Normal Mode
Aside from the usual increased health and damage associated with all Heroic modes, there are two key differences in the mechanics of the fight, one in each phase.
- Immerseus Phase
Once per Immerseus Phase, the boss gains a buff called Swelling Corruption (the boss will cast this spell more than once if you spend enough time in the phase, but the cooldown is so high that this is unlikely to ever happen). Swelling Corruption has an unlimited duration, and it has a certain number of stacks. Specifically, the buff has one stack for every 2 points of Corruption that the boss has. This means that the very first Swelling Corruption has 50 stacks, and then each one has fewer and fewer stacks as the fight goes on.
Every attack made against the boss removes a stack of the buff, and causes the attacker to gain a stack of a dispellable 6-second Shadow-damage DoT, and to spawn an add called Congealed Sha. The DoT's damage increases over the course of its 6-second duration, and the Congealed Sha adds do not do anything except melee their main aggro target. Swelling Corruption has no other effects, and once all of its stacks are gone, it disappears.
- Split Phase
During the Split Phase, Immerseus gains an ability called Sha Pool. This causes the center of the room (the area where your raid cannot go without being damaged and knocked back, and the same area where all the adds converge) to become a large void zone. Any players standing inside the void zone take a small amount of Shadow damage every second. The void zone grows slowly over the course of the Split Phase, and it also grows each time a Sha Puddle, Contaminated Puddle or Purified Puddle reaches it. As it increases in size, its damage is also increased. The void zone shrinks in size whenever it damages a raid member, and it disappears as soon as the phase ends.
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) here is a tact i thought about from what i notice from last night tries... for start i will point some fact:
here how i see we can swap boss and adds with more controling