Controlled by Zovaal, Dausegne leads the mawsworn in a battle to gain control of the Forge of Afterlives. With its power, The Jailer will be able to create an eternity of torment.
This is a single phase encounter which does not have many mechanics but has them happening in higher frequency as the fight goes on.
You will need to dodge Halos which come from Corrupted Pillars, and every time the boss runs out of Energy it will corrupt a new pillar which in turn creates an additional Halo each cast.
Every time the boss teleports it will apply an absorb shield which needs to be broken to deal substantial damage to the boss.
Disintegration Halo - When you move through a Halo you will receive a debuff that increases your damage taken. Wait for this to fall off before running through another.
Obliteration Arc - Dodge this beam. If you are caught in a bad spot use a defensive.
Staggering Barrage - A random non-tank player is targeted by this and the damage needs to be split with other players. Soaking this will apply a debuff so you are not able to soak two in a row. Soak these when you do not have a debuff.
Inevitable Dominion - When the boss runs out of Energy it will teleport to the next Reservoir and apply a shield. Break the shield to remove 10% health from the boss.
Infused Strikes - Stacking tank debuff when being hit by the boss. Swap on ~4-6 stacks. When this debuff expires it will trigger 
Unleashed Infusion.
Domination Core - These adds are a DPS Priority. If you are not tanking the boss, tank this mob. Try to keep it slightly away from the boss as it spawns pools that last for 2 minutes.
Dausegne Swing Timer: 2s (Curse of Weakness 2.4s)
Transcendence can be useful to teleport over a Disintegration Halo and not receive a debuff.
-
Blessing of Spellwarding and 
Divine Shield will prevent you from receiving debuffs from Disintegration Halo.
Domination Bolt, Obliteration Arc and Staggering Barrage can be reflected with 
Spell Reflection.
Rallying Cry is best used to provide EHP to the raid for Inevitable Dominion.
Stampeding Roar is useful to get players in position for Inevitable Dominion or to help people move large spaces to survive Disintegration Halo or Obliteration Arc.
If you are a Night Fae consider saving your 
Convoke the Spirits to break the 
Siphoned Barrier.
If 
Anti-Magic Shell is active as you run through a Disintegration Halo you will not receive a debuff.
Anti-Magic Zone is best used to mitigate raid damage taken from Inevitable Dominion.
This is a single phase encounter which does not have many mechanics but has them happening in higher frequency as the fight goes on.
You will need to dodge Halos which come from Corrupted Pillars, and every time the boss runs out of Energy it will corrupt a new pillar which in turn creates an additional Halo each cast.
Every time the boss teleports it will apply an absorb shield which needs to be broken to deal substantial damage to the boss.
Bloodlust/Time Warp/Heroism is best used on Pull.
You should have groups set up for Staggering Barrage soaking and Cooldowns pre-assigned for Shields.
I'd recommend just simply splitting the raid in two and having half of the raid assigned to soak at a time. That way it's not a big deal if a few people miss due to being out of position or having a debuff by being a target of the spell already.
The boss runs out of Energy just over every 2 minutes. This means that defensive cooldowns such as Anti-Magic Zone are available for every Shield.
If your raid DPS is inconsistent it may be worth considering assigning some 2 minute DPS specs such as Retribution Paladin, Mage or Hunter to the Shields.
Disintegration Halo - The boss will periodically spawn Halos from reservoirs it has corrupted. You are able to see the locations Halos will come from by keeping track of the Shadow orb the boss fires. This will be useful later in the encounter where you can have up to 4 Halos per cast.
Pay close attention to the orbs flying from just above the head of the boss.
When you move through a Halo you will receive a debuff that increases your damage taken. Wait for this to fall off before running through another.
Obliteration Arc - This beam is targeted at ranged players. Simply move out of the pattern that is created. If you are caught in a bad spot use a defensive.
It is possible to bait the beam however the exact number of players required seemed to change each test. Once this has been determined on Live this will be updated.
Staggering Barrage - A random non-tank player is targeted by this and the damage needs to be split with other players. Soaking this will apply a debuff so you are not able to soak two in a row. Soak these when you do not have a debuff.
These can be solo soaked with an Immunity (on the target of the Barrage).
Inevitable Dominion - When the boss runs out of Energy it will teleport to the next Reservoir and apply a 3% Health Shield. Whilst this Shield holds there will be pulsing raid damage. If you break the shield the boss will lose 10% Health.
When a new Reservoir has been corrupted Halos can now spawn from that location.
Infused Strikes - Stacking tank debuff when being hit by the boss. Swap when you are on ~4-6 stacks and your co-tank does not have any stacks.
When this debuff expires it will trigger Unleashed Infusion based on the amount of Infused Strikes stacks you had.
Domination Core - These adds are a DPS Priority. If you are not tanking the boss, tank this mob. It will spawn 
Encroaching Dominion pools around itself. Avoid these pools.
The pools tick instantly so you want to position the add in a way that it doesn't hit melee as if this lands at the same time as them crossing a Halo that can lead to a quick death.
Dausegne Swing Timer: 2s (Curse of Weakness 2.4s)
Transcendence can be useful to teleport over a Disintegration Halo and not receive a debuff.
-
Blessing of Spellwarding and Divine Shield will prevent you from receiving debuffs from Disintegration Halo.
Domination Bolt, Obliteration Arc and Staggering Barrage can be reflected with Spell Reflection.
Rallying Cry is best used to provide EHP to the raid for Inevitable Dominion.
Stampeding Roar is useful to get players in position for Inevitable Dominion or to help people move large spaces to survive Disintegration Halo or Obliteration Arc.
If you are a Night Fae consider saving your Convoke the Spirits to break the Siphoned Barrier.
If Anti-Magic Shell is active as you run through a Disintegration Halo you will not receive a debuff.
Anti-Magic Zone is best used to mitigate raid damage taken from Inevitable Dominion.
The big change to this encounter outside of increased values on every spell is that Disintegration Halo will now cleave damage to anyone within 1 yard. Yep you read that right, 1 yard. Seems kind of minor, but it can be quite problematic as you're fairly limited on space when moving through those Halos later in the encounter as you're trying to manage multiple in a short span.
The only things to assign are the same as they are in Heroic.
Cooldowns for Shields & Soakers for Staggering Barrage.
This section will be updated once the boss has been defeated on Live Servers.
The change to the Disintegration Halo means that when you pass through the Halo you create a very small AoE splash around you. If anyone is inside that area (as shown in the video below) both you and the other play will take a lethal amount of damage.
In terms of strategy for the encounter this does not change all too much from Heroic. You will just need to be mindful of other player positions. It may however make you want to consider a total cap of Melee DPS to bring to the encounter for a first kill.