The Prophet Skitra
This fight consists of two phases, the boss phase and the illusion phase. Every 20% health the boss looses it will create Illusionary Projections of itself and each half of the raid (each tank will see different illusions) can see 4 of these illusions each. Two of these illusions will be on the same location so tank communication is required to uncover which is the real illusion.
Phase 1 (Boss Phase)
Shadow Shock - This is the only ability the boss will cast on the tank, there is no melee swing. This applies a debuff on the tank which increases Shadow damage taken and deals damage to the tank + 2 random players. You should swap tanks when the debuff falls off (~4-5 stacks).
Shred Psyche - This is the main mechanic of the phase. The target of this debuff will have a 5 seconds to get into position, when this debuff expires an add will spawn and begin to cast Psychic Outburst which will deal damage based on your distance from it. After this the add will channel Psychic Reverberations which will deal Shadow damage every 1.5 seconds until defeated.
You are able to displace and root these images (same as Coven of Shivarra in Antorus).
After 30 seconds their Intangible Illusion buff will have expired, making them vulnerable to taking damage and can be removed from the encounter.
Your group will want to use their utility to keep the path that you are standing in clear of adds so you are able to negate the mechanic in it's entirety.
When the boss looses 20% health, it will transition into Phase 2.
Phase 2 (Illusion Phase)
Each half of the raid will see 4 illusions of the boss each. Luckily, the tanks are always given separate debuffs, so you can just communicate with each other whilst the raid waits patiently for the call on what to hit.
There are multiple strategies you can do for this phase, this example is what worked best for me in Mythic PTR testing. As shown on the map above, each tank will place 4 raid markers on the floor, where there are two raid markers this indicates that this Illusion is real. Likewise if Tank 1 can see a marker on an add that Tank 2 has placed they can call this out and place a marker down on it to help speed things along.
Tank Damage Profile
Swap when your Shadow Shock debuff expires (~4-5 debuff stacks)
Be ready to mark adds in Phase 2 and communicate where necessary.
[Heroic] Ring of Peace is very useful to create a path for the raid on Image of Absolution
Vengeance Demon Hunter
Fiery Brand will reduce the damage taken from Shadow Shock
[Heroic] Sigil of Chains is very useful to create a path for the raid on Image of Absolution
[Heroic - UNTESTED] Sigil of Misery can be used to stop the Image of Absolution from moving temporarily
Holy Shield is a must have on this encounter as there are no auto attacks; it's all magic damage
Blessing of Sacrifice can be used on your co-tank to reduce their damage taken
Rallying Cry is a powerful raid cooldown to use during Phase 2
[Heroic] Mass Entanglement is very useful to create a safe area for the raid on Image of Absolution
Blood Death Knight
[Heroic] Gorefiend's Grasp is very useful to create a path for the raid on Image of Absolution