If it is so mind-numbingly easy I think its probably a case of :
"Oh no! Crystal tower is too easy at level 90 wth my ilvl 500+ gear!"
Possible solution: mayhaps if they set a maximum ilvl and you need to be below a certain ilvl to participate could add to the challenge.

or you have run it so many times you know the mechanics by heart and never fail them.
Possible solution: have bosses switch between 3-4 mechanics randomly each run might make it a bit more challenging to run.

IDK I've died countless times in these alliance raids because I didn't know the mechanics.

"Oh, group B needs to get swallowed by Cerberus!"
.. oh ok.. *dies horribly*
"Oh, you need to stand in one puddle of vomit to get shrunk then stand in the other puddle of vomit.."
.. Oh. Ok..