I would say these things about the concept of difficulty here endgame.
I would say the most straightforward and honest difficult parts in my experience are lost dungeon and mu. Lost dungeon has been difficult and I know it might be save or die or quick defeat, but I wonder if I really had a chance there or if it's just me accepting if it didn't go my way it's done. I suppose I've done some lighter farming there with my paladin before. It might be based entirely on luring though, since we often don't want to face the entire crowd.
Mu those bosses are sometimes more difficult than Mu itself and everything just stops sometimes cause it's like diamond golem boss or death stalker boss.
Trighton death vault is kind of weird when done with a group of elementals and more it could be difficult but it could also be ummm, wrong maybe. I think I recall one time we hung out by the stairs I was iron golem and it was okay for a while. Gotta hang by the stairs though. The portal upon entrance to a random place might be a bad thing if you have to sanct or something to the stairs where a group can be formed.
Sendauntra, I've only had difficulty in web when we tried to do it, and eye of death when done with melees or something.
Grubs might not be difficult, but I always feel it can be a bit intense. Also it gets tense when you are doing a melee and a bunch show up or ts goes down.
Forgies sanctum might be the most difficult in forgies, but I do have something to say about that. A lot of the times there it is going fine, and then 2 or 3 templars show up and it is like full retreat or defeat due to the templars. I think the templars in forgies sanctum are like the entire thing really maybe. From my experience at least.
Darkmoor really only temple when sanct wailing it can be a bit difficult heh, and sanctum is annoyingly difficult like in forgies due to the random spawns it has. I've always told people if you want to do darkmoor sanctum it is better to just retreat after a while to rest in interiors, because the random spawn is going to mess you up when resting most likely.
I also remember behind the gate in upper darkmoor, but I don't want to talk about it without remembering that the people from below the gate can shoot across everything to where you are, which can be annoying.
So I feel like some of these might be too overwhelming. Grubs seems not difficult but intense. Forgies sanctum and places in darkmoor can be annoyingly difficult. I like how sendauntra people at least know that they are getting into it in web when it happens.
I'm not sure about dungeon because I feel it can be based entirely upon luring or bad rests. I remember often in a group we can storm by, and then we get spawned apart by map change sometimes. Dsipel happens often there. It seems more like it could be said to accept the overwhelming nature of the game, and then as such requires teams because of it? That would be my guess as to dungeon.
So I guess I've liked grubs, sendauntra web, and Mu.
What I said above about the strategy part, now that part was also fun. I remember I did testing pit with melees before and it was a bit difficult but also we used a safer strategy which was the entire thing. But yeah we used drones as 3 melees and an archer and were still pushed back behind the ramp. That was a bit fun and difficult I guess. Breeding pit might've had a same experience.
Pit is just too over the top crazy sometimes heh.