Nightmare Nefra, Who Bars the Way

Nefra, Who Bars the Way | Gate Commander Draxus | Grob'Thok, Who Feed the Forge | Corruptor Zero | Dread Master Brontes

Mechanics:
Enrage Timer

190 seconds

Nefra, Who Bars the Way Health: 2,575,224 Twin Attack Kinetic Cleave (M2) Nightmare Twin Attack Kinetic Cleave (Mx) Voice of the Masters Internal Raid DoT

Twin Attack
Like SM/HM, tanks must stack to mitigate Twin Attack cleave damage. Each Twin Attack builds a stack of Nefra’s Curse on the offtank.

At 5 stacks, the offtank will take 200% increased damage. Tank swap around 3-4 stacks to drop the debuff.

Nightmare Twin Attack

Each time Nefra uses Twin Attack, she will gain a stack of the Nightmare Twin Attack buff. 

At 15 stacks, Nefra will channel Nightmare Twin Attack, a massive frontal cleave hitting anyone in her path. Nightmare Twin Attack is a meteor-like effect, doing less damage to each person based upon the number of people hit by it.

At around 12 stacks, the entire raid group should stack behind the boss. At around 14 stacks, the raid should prepare whichever strategy they decide to mitigate the Nightmare Twin Attack damage with (SEE Stack to the Tanks/Tanks Stack to the Raid below). The cast of Nightmare Twin Attack is 1.5 seconds long, during which all eight players should remain stacked, popping defensive cooldowns (Scrambling Field/Ballistic Shield) to mitigate the attack.

Voice of the Masters (Any)

Cleansable internal raid DoT that functions identical to hard mode, but deals more damage.

Overloaded Assault Droid

Has the same Reactor Overload (red circle) channel time as hardmode (~5 seconds) but sometimes charges/hits its intended target before it begins channeling. Does not appear to happen 100% of the time; negligible damage (if any).

Strategy:

Overview

This fight (in its current form) is not all that much harder than hard mode. This fight requires minimal awareness, though it may be beneficial for a tank or dps to call out Nightmare Twin Attack for the healers. As in hard mode, cleanses are important, and they deal the vast majority of the damage to the raid.

Setup
As in hard mode, set up with plenty of room to spread around. Both tanks should stack on each other, and may benefit from focus targetting the other tank to keep an eye on his debuffs and call out if he needs to be taunting. Melee should each take a leg of the backside of the boss. The remainder of the raid should spread out as much as possible to minimize the movement required during the Overloaded Assault Droid's Reactor Overload. If you raid group prefers stacking and moving together, Nightmare mode still allows for that, but be weary that your damage will greatly suffer as a result and the stack-and-move method is essentially a cop-out for lazy healing.
Pre-assign who is cleansing who for Voice of the Masters, ideally with no one person cleansing more than three targets.
Also decide how your group will handle Nightmare Twin Attack and the required stacking. It can be handled essentially one of two ways:
1. Stack to the Tanks: Our preferred method, as trying to pivot Nefra quickly can result in her running around haphazardly and may unintentionally get people killed. At 13 stacks, have the entire raid group stack behind the boss. At 14 stacks, right before the transition to 15, hop in front of the boss. This will minimize any chances of Twin Attack cleaving, and will leave plenty of time to take the hit. 
After the Nightmare Twin Attack goes off, DPS and healers quickly leave from the front of the boss (before a Twin Attack cleave goes out) and proceed to your usual positions.
2. Tanks Stack to the Raid: (See above for why this can fail you) At 13 stacks, have the entire raid group stack behind the boss. At 14+ stacks, the two tanks move together and pivot the boss to face the raid group. Make sure both tanks stay glued to one another to share any Twin Attack cleaves along the way.
After the Nightmare Twin Attack goes off, tanks quickly turn the boss to its previous position. DPS and healers can then move back to their normal positions.

Inspiration/Bloodthirst Because the duration of the fight only allows for one use of the ability, it is preferred to use it sub-30% of the fight, as it will allow for execute-style abilities to be used. Alternatively, if the raid composition possesses few execute abilities, using it shortly after initiating the fight is preferred, as the max number of attacks will be off cooldown.