Did this last week.
Had a Wizard, Rogue, Necro and myself boxing Paladin/Cleric.
Steam rolled everything up to sisters. Had some trouble with sisters due to only 2 people knowing how to do the hails/responses the other person I tried instructing failboated hard :/.
Eventually had 2 Necros, Druid, 2 Clerics, Rogue. With Druid / Rogue / Necro on hails, 2 clerics tanked all the mobs and necro owned them.
Did Devlin/Tris with same combo (swapped druid back for paladin here) and Tris dropped page.
Went back later did Roley with Paladin, Cleric, Bard, Necro
Then I two boxed Perfomer with Paladin, Cleric.
Later that day went back yet again, did Mayong with Ranger, Cleric, Paladin/Bard, Wizard, Beastlord/Berserker and got my alt his 2.5 page $.
Demiplane events that give most people trouble are Sisters and Performer. Anyone should be able to steam roll ZiThuuli, Redfang, and Hatchet if you have 3 or 4 level 90 toons that are competent.
Sisters takes a bit to get used to but if you have a brain the event is very easy just involves lots of moving around / tracking for where they warped to. It is almost impossible to box this event I'd say, need to get 2 competent friends to help ya on this one.
Devlin and Roley are pretty easy (Roley kinda blows if you don't have a class for the warrior, bard, rng, rogue bane clicky since that is about 75% of the ports).
Tris is easy but it helps having mass numbers of people, when we did it, I played the Paladin/Cleric... only 2 healers in the raid and would often get charmed x 2 during the live phase, which is insanely frustrating. So if you can just add as many bodies as is feasible to eat those charms so your priests don't get charmed while trying to heal up to 100% then RGC in a short window. Having just a group can royally suck on this event. Even less blows more.
Performer you either need to be a quick typer / have hotkeys to not fail that one. I've gotten to the point I just don't bother teaching new people how to do them and I just box it on my own its faster that way unless people have done Demiplane before. Generally teaching people through this will take 1-2 wipes until people figure stuff out.... depending on how smart the person is tbh. I've been on raids where I've just told someone they are too stupid and to camp out and log back in in 20 minutes when its won because they are bringing us down :/.
Mayong is a straight endurance fight. Kinda blows for casters because most of them are really resistant. Have a strong tank if you don't have an AoE root class for the bats otherwise those can be a pita. Sadly due to page drop rates, Mayong is the best avenue to getting your 2.5 page. Just setup your hails:
Title: The Dark Savant
Loot: Invocation of Night
Answer Irrissa the Seer: Disgusted
Answer Ariahn Teller: killed her ability to love
Answer Ur-Koraag: forget
Answer Arturos, Trainer of Bats: control or destroy
And that guarantees the Necro 2.5 page to drop 100% on successfully killing Mayong -- If you do all those answers correctly and trigger on the character that does the answers -- Plus you get a suffix 'The Dark Savant' which is pretty awesome imo.