It sucks the story was so bad this expansion, but Im honestly really enjoying the EX fights, I really wish we'd do another set of organized thread FTs again though, that was a ton of fun!
I haven't done ex5 yet but so far I would say EX4 and EX2 are the hardest.
2 because of the swapping swords mirroring onto the ground the circles of confusion
Ex4: Dear God particle effects and movements and body checks. I hate Eschelon's Fall and I think it's bloom 5 where the boss turns yellow and you have to go from one side to a specific area.
I think ex3 and EX1 have nice looking stages