Important Trash
Probably the scariest parts for Priory, are the 206704s and 217658.
For the 206704s the most important thing you have to know is that 448791 has a forced cooldown of five seconds between casts, so it doesn't matter how many of them you pull at the same time, you will never get more than one 448791 every five seconds. However it does mean that you will get these back to back with five seconds in between each times as many paladins as you pulled
For a normal pull with two 206704s you should expect to have your group at full hp before the first 448791 and top them quickly after it to take the second 448791. After that you will have downtime before the cooldown from the first casts comes back up and you have to start healing this damage again. A good way to deal with these is just lb. You can spread echo in your group beforehand, once the first 448791 hits, use ve on these echoes and prepare to cast a sb into the lb, which can land right after the second 448791 hits the group, letting you heal both damage events with a single ramp.
It is common for 206704 pulls to also have some 206697s in them, which means a very important thing to consider is someone can die from the 448791 if they get hit by 427357 at the same time. You can avoid these scenarios by either interrupting or stopping casts at the most dangerous moments, or by using td or tg proactively on people being targeted by it.
As for 217658, at a certain key level you should plan on using lust on this guy. The damage intake is very high and the longer you have to deal with it the more likely you are to fall behind, run out of cooldowns and cause a wipe due to lack of healing. Remember to start the pull with stasis as early as needed as it is likely you can have it back one more near the end of the fight unlike other longer cooldowns.
You should do into it knowing you are gonna need to do a lot of healing and having a basic idea of how you are gonna rotate between your cooldowns, remember that stasis does nothing if you don't have your empower spells available to fill it and ec can't save you if you haven't ramped echoes beforehand. Be several steps ahead of the damage at all times and you should be fine.