Hello everyone ! Today, in what will probably be the only T16 Mage solo until WoD, Immerseus 10 man normal mode !
The strategy itself it quite simple. When nobody is in melee range, Immerseus will spam his Corrosive Blast (600k shadow damage and +300% shadow damage taken) in front of him, normally killing anyone in 1 or 2 hits. But pets are completely immune to it, so all you have to do is position your pet outside of melee range, stay away from the cone infront of Immerseus, and stay farther than where your pet is so Immerseus never picks you as a target.
The fight itself is pretty simple : approximately every 5 seconds, Immerseus will use Sha Bolt. It does 15k damage, and creates a Sha Pool under your feet, which does 75k damage for every second you stand in the AoE. Every 30 seconds, Immerseus will use Swirl, doing 150k damage per second in the water (careful, you can take multiple ticks sometimes). Once you reduce his HP to less than 1M, Immerseus will Split, creating multiple adds, some you can kill, others you can heal. Kill as much as possible, each kill removing 1 corruption from Immerseus, and P1 restards, with his HP percantage equal to his current Corruption (58 corruption = P1 with 58% HP)
At the 10 minute mark, Immerseus will Berserk, increasing his damage by 900%. Fortunately, only the abilities directly used by Immerseus are affected : Sha Pool damage is still 75k (and not 750k, which would have been much more of a problem), but Sha Bolt now does 150k. Add it to the 75k tick you always take, that's a 225k damage every 5 seconds, more if you stay in the AoE. Swirl now does 1.5M and must of course be avoided.
The Berserk lasts 30 minutes, after which Immerseus does his initial damage and never re-enrages (phew).
Some tips :
You will need a very good gear. This fight is more about DPS than survivability, but you will need a good DPS to survive. Iron Juggernaut trinket is an absolute requirement (does around 40% of the healing).
During Berserk, every time you step out of an AoE, you MUST Evocate at least once before the next one. If you don't, you will quickly be overwhelmed by the damage. Take the time to heal yourself.
Never get hit by Swirl, even when Immerseus is not enraged. This ability is bugged to the core, sometimes dealing 5times the damage, or even making the game believe you are standing in a Sha Pool even if you're not. Blink to the wall and stay there, unless you are sure Swirl won't reach you.
Never move your pet. Let me say that again. NEVER move your pet. During transitions, your pet will follow you if he can't reach the adds you are DPSing. If he is not far enough of the boss when he respawns, Immerseus will 1shot your pet with a melee and 2shot you with Corruption Blast. Don't get too greedy to reach far away adds in transitions, so during Iceblock you have time to send him back to his original spot.
Cold Snap is required for every transitions, since adds explosion deal massive damage. Near the end of the fight, don't hesitate to stop DPSing the boss completely to wait for the cooldown.
Fight ends at 10 energy, not 0, to my complete surprise, never even noticed that.