233815 is a very weird boss. During the whole of phase one you will not find a single good spot to use your engulfs or stasis as the fight mostly involves light rot damage and spot healing specific targets assigned to mechanics at the time. You need a specific mindset going into this boss that what your brain is used to as good Preservation play doesn't really apply fully here, as your normal healing pattern just doesn't fit what the fight does for most of the time you're gonna spend progressing it
Phase One
The are three important sources of damage during phase one:
- 1231408 will constantly deal low amounts of damage to the whole raid, this is not really dangerous and noone is ever at risk of dying from it but because it happens constantly and to everyone it will be the highest individual source of damage during phase one.
- 1226315 will bind several players to the middle of the room, dealing increasing damage until they reach the edges of the room. This takes a bit of time because the raid has to kill the 245173s in order for people to walk out of the middle of the room, so the damage will ramp up and eventually become very dangerous. This is the main thing that will kill people during your progress as walking to the edge of the room while taking very heavy damage from the 1226315 and dodging 1226395s is complicated. You can try to lb these people once the stacks reach high numbers in order to help keep them alive.
- Finally, 1247672 will need to be soaked by players, taking ramping up ticking damage while they soak the rays. This is not as dangerous as the 1226315s because people can simply side step to either side and instantly stop taking damage from it, but you should keep an eye out for these players as they will be taking heavy damage and need some amount of healing in order to be able to soak the whole pylon and avoid raid damage.
The main issue with this phase is how you try to fix the conflict between three things: first how you are used to playing the spec, second what would actually do more healing in this situation, and third what will prevent more people from dying and thus speed up progress the most.
Your muscle memory might tell you to lb and do big ramps for engulf, but considering what the main damage source is you would get much more mileage out of simply echoing as much db as possible. On the counterside, the biggest damage source is not what actually kills people, and instead if you want to avoid deads and take your raid alive into phase two you would be better of single target focusing the 1226315 targets, even tho this would mean you do very little overall hps.
I leave it up to you to decide what you think is the most important part for you, but i really don't think there is a single satisfying answer.
Phase Two
Once the boss reaches 50% health, it will drop down to the ground and hit the whole raid with 1228059. This only happens one time at the start of the phase and it's not very dangerous, but you should immediately prepare for the following mechanics:
- 1227226 is a frontal cone that has to be soaked. Any one person can only soak every other so the raid will be split into two groups and alternate between who soaks every frontal.
- After every soak, 1227782 will be cast and the whole raid will take damage while having to spread apart and being pushed back slightly.
You should prepare for constant high damage happening to the raid non stop during phase two, however none of these mechanics really fit what you want to do as Preservation: the 1227226s only hit half the raid and the 1227782s forces the raid to be very spread apart, so consume and essencebomb don't work as well as they should for either.
It can be a very good idea to plan to lb ec on the whole raid during 1227782 as range for it doesn't matter, and this is also a good place to split your stasis store and release as it is unlikely that you need to quick release to cover the damage.