This encounter relies heavily on individual player awareness and understanding of how the mechanics will affect them.
1 – Appendages all have 13 million health. It takes a raid approximately 30 seconds to burn one of these down, assuming all dps are hitting the same target. If that appendage is debuffed with volatile seed (the tank debuff, an orange circle that is locked to the tanks until it expires), the appendage takes 60% increased damage. This means you can kill an appendage in under 10 seconds. There are multiple instances where two or more appendages will be debuffed, meaning in theory, your team can clear out multiple appendages in the same time it would take them to kill a single appendage.
2 – Raiders will be tempted to focus the most convenient appendage for them to hit (ranged will want to hit eyes or maws, melee will want to hit tentacles). Appendages on 1% health do as much damage as an appendage on 99% health. Additionally, the only way to do damage to the boss is to actually kill appendages. For this reason, except for very specific appendages indicated in the video linked, the entire raid should be focused on blowing up one appendage at a time.
3 – As a general rule, 4 appendages of the same time represent an existential threat to the raid. The strategy calls for, generally, the raid to move in a clockwise circle around the room, clearing appendages to prevent the raid from being overwhelmed.
4 – The most obvious threat are the tentacles and their Entropic Crash ability, which does massive damage to any player nearby, and around 200k damage to all raiders minimum. Drest will also count as a tentacle when an Entropic Crash goes off, meaning a total of 800k damage. There are two specific occasions where three tentacles will be up during an Entropic Crash; 7:30 and 8:15, these will need large healer cooldowns in combination with the raid evacuating to the safe zones to survive.
5 – Speaking of safe zones – the raid is asked to kill appendages in a specific order. This allows for the existence of safe zones – places in the room where there are no tentacles, and the raid can flee to during 2+ tentacle crashes. Minimising avoidable raid damage is part of being a good raider.
6 – Once crashes are understood, the main raid killer is Mutterings of Insanity (purple circles on raiders). These can and should be dispelled. A raider affected by Mutterings is rapidly slowed and immobilised. While they should make every effort to move to safety as soon as possible, raiders must be prepared that not all Mutterings will be dispelled and should move away themselves.
7 – There are two occasions where melee are asked to focus down Maws in a very short time frame. Melee should take care not to allow their Mutterings of Betrayal to hit 4; and must move out if they hit 2 or more stacks.
8 – Other than that, it’s up to player responsibility. Blow up the appendages marked by the tanks. Tanks mark the correct appendages. Pick up blood and tunnel the boss; once your blood has expired, switch back to appendages. Above all, avoid focusing the boss blindly.