Every mechanic on this boss comes with some sort of healing interaction. Let's focus first on the threats on the entire group. Obsidian Beam is a tank mechanic with an AOE Burst that spawns laser beams to dodge. Some might say it is a bit much for a singular mechanic. It also happens every 25 seconds. You could find yourself out of range from your team, try to prepare ahead of time as healing during the beams rotation can be challenging.

The other big group mechanic starts with the Burning Shadows debuff. When you dispel it, it will drop a healing absorb on every player. The danger comes when this overlaps poorly with the other mechanics. It is on a 16 seconds cooldown, but it gets delayed by spell queuing quite often (this fight is very fast paced)

The last source of damage is Collapsing Night (the shadow circles). They will need some spot healing on the two victims, make sure that you anticipate who the targets are. This happens every 25 seconds, always just a few seconds before the beams. Help yourself and be ready to interrupt the boss right after that so that he does not sit in poop during the beam.

Overall this is a very tough fight, and you can pretty much rotate your cooldowns. You can use them agressively as you get a breather with Darkness Comes to recover them. Also make sure to keep your maintenance heals up at all time.

Anub'Ikkaj has 2 main mechanics you should be worried about. Even if well handled, the Dark Orb will create a burst of damage. As is always the case for 1-Hitters, the main concern is to make sure people are high enough before the hit. The spell queuing can lead to the spell being cast much less than that, but the cooldown really is 16 seconds. In any case, you get quite a long animation to be ready.

One way for Dark Orb to get dangerous is if it is immediately followed by Shadowy Decay. It is your standard burst mechanic, and ticks pretty hard. Make sure to be ready for it. It has a 35 seconds cooldown. This is the primary mechanic to line up your cooldowns with.

During the first phase of the fight, your main concern is Erosive Spray and the Lingering Erosion it leaves behind. It creates a surprisingly long (15 seconds!) wave of damage on a 28 seconds timer. By the time you fully recover, the next wave will probably be upon you.

You can pretty much consider this phase like a Rot fight and rotate your cooldowns, just make sure not to pop everything during the short down phase :)

P2 still includes Erosive Spray with a slightly longer 31 seconds cooldown. However it also adds Spinneret's Strands (26 seconds cooldown) which will create 2 hits on the group when the targets break their web link. Make sure that everybody is topped enough to survive the hits.