This is a very good fight for Preservation in my opinion. There are several instances of high raid-wide damage and healing absorbs happening at decent gaps from one another and the raid is very closely stacked all the fight which makes it perfect for consume and essencebomb.
The fight doesn't really have phases, you will simply go thought a scripted sequence of dealing with some adds and then the remaining ones breaking out before starting again. There are several sources of aoe damage like 1246775, 1227848 and 1242088 sprinkled through the fight and your goal here is to fit as many usages of stasis and engulf on as many of these events as possible, taking note that 1242088 will knock everyone backwards.
Because of the way these three spells line up the first two times they happen every set, your stasis and ec can be used together in an specially good way to take maximum advantage of your spells
This way, you can use the ta stored in the final slot of your stasis to quickly ramp up to 15 or more echoes to lb ec for 1242088, while also having two engulfs healing the whole raid with consume flame on both 1246775 and 1227848.
As for how to fit the rest of your individual engulfs and stasises across the fight it is somewhat important that you coordinate this with your co-healers, as the fight constantly drops damage on everyone and while you as Preservation have very good coverage you still want some extra oomph on certain moments where you aren't using very powerful things like only df
Plan your cooldowns ahead of time for as many of these big raid wide hits as possible and abuse stasis release timings to widen your coverage as needed to keep healing even more mechanics and you will find yourself doing very high amounts of healing.
An important note to keep in mind is that due to unshakeable you do not want to be casting a healing empower when the boss uses 1242088 otherwise you will immune the knockback but still drop a puddle out of position.