From laughably trivial to completely insane, that's the definition of Mythic Emerald Nightmare.

Nythendra 0:00 : Pure and sheer luck. If you are not in a tanking spec, she will cast Infested Mind after Infested Breath, killing you if you have 10 or more stacks or Rot. This is inevitable
Here comes the dumb part : 90% of the time, Nythendra will use Rot just before the first Infested Breath, inevitably pushing you at 10 stacks and ensuring you will die when she casts Infested Mind. If that was consistent, you would have 45 seconds to kill here, which amounts to 60k of DPS required to kill her before this. Completely impossible.
But, SOMETIMES, she will decide to use Infested Breath without casting Rot first. If you don't slack in P1, that should leave you at 9 stacks for the first Infested Mind, and then you have a lot more time. The DPS required goes down to 30k, which is easy with gear. This strat works with all classes and only requires patience.

Elerethe Renferal 1:45 : Trivial. Don't stand in the web though.

Dragons of Nightmare 3:48 : Very easy, but be careful : the Lumbering Mindgorger is still very much there, so you have about 1 min 30s to kill this boss. Nevertheless, with Splitting Ice it is very easy.

Il'gynoth 5:14 : You don't actually have to push him in 1 phase, I just did it for fun. Very easy fight.

Ursoc 7:30 : Insanely high damage. Overwhelm increases all damage taken by 15%, and Rend Flesh by 250%, by stack. This makes Rend Flesh deadly at anything over 3 Overwhelm stacks. I use Mirror Image to avoid tanking at the start, and I get them back a split second before the Rend Flesh cast that would have killed me. Ice Block is saved to remove both debuffs. I also used Engineering Nitro Boosts to avoid taking too much damage from melee, not sure it is really necessary, but the DPS check is not high anyway.

Cenarius 10:22 : Did you notice my ivl was 394 ? That's not a mistake : I forgot to equip my boots and did the fight with ilvl 58 engineering nitroboosts. That should tell you something about how easy this boss is.

Xavius 12:39 : Pure DPS check. Take dream at beginning, save cooldowns for when you have 100% energy, do it twice, GG.

The difficulty of this raid is extremely uneven, you can get stuck on the very first boss while the last boss is trivial. Fortunately now it's over !

Music :

Zayde Wolf - Born Ready
https://www.youtube.com/watch?v=dGdHA...

The Score - The Fear
https://www.youtube.com/watch?v=K5U7b...

Roby Fayer - Ready To Fight (Ft.Tom Gefen)
https://www.youtube.com/watch?v=dy-5e...

The Score - Born For This
https://www.youtube.com/watch?v=aJ5Iz...


Enjoy :)