Skolex, the Insatiable Hunger
Please see https://www.wowhead.com/guides/skolex-the-insatiable-ravener-encounter-journal-boss-abilities-raid-loot for full information.
Setting up:
Two raid markers, one under boss, one 30 yds away in direct line.
Create two groups of three ranged players to be furthest away from the raid.
30 yd marker is location of 3 ranged group, and Debuff removal.
Brief Tactics:
Bloodlust on pull.
Tanks stack together (boss will often hit tank and next closest raider, who should be other tank).
Stay *fairly* close to the boss to make it easier to avoid the very large frontal cone.
Blue swirlies within 20yds of boss .. avoid blue swirlies (cause damage and massive haste reduction).
Everyone is gaining Ephemeral Dust Debuff. Only way to get rid is by the boss burrowing under you.
Boss will do additional dust attack to 3 furthest players (it does 10 yd splash damage so spread a bit). Alternate 3 furthest players on frontal cone attack.
At 100 energy, tanks split a little and taunt swap - don't ever get hit by two back to back hits of the same attack (Riftmaw or Rend). (on heroic this generates a frontal cone, so keep facing away from raid).
Fight Flow:
Tank combo > dodge frontal (swap back 3) > tank combo > dodge frontal > stack for buff removal. Repeat.
Note that each stack for buff removal the boss gained 10% increase in damage.