It seems like only the tank one is tuned for that high, most other classes are getting it in 20-30 attempts. My wife who is not a great player finished hers as assassination and is very close on the outlaw one. she parses mid-50's in our Heroic runs so the dps checks for the dps are actually lower than the tanks.
I did the windwalker one last night and im able to get the tauren down and the wurm down pretty low - feels infinitely doable if i clean up my rotation and maximize my cooldowns. i also did pretty well on the mistweaver one, and i've never played mistweaver except in an odd Battleground, i would need a bit more gear here since i was still wearing mostly tank gear.
the tank one still feels like a kick in the face compared. I'm getting buggy attempts where after 4 minutes velen has only dropped 2 orbs and im getting attempts where i push the inquisitor down super fast because velen drops 5000 orbs. I've had attempts where infernals turn mid slam cast and ive had attempts where the eyeball pulses dont show beams and just knock you off the platform. i had ~30 attempts last night but it still feels blatantly shitty atleast 10 of those attempts were wasted because of shitty bugs or just shitty rng on orbs. i've had probably 5 or so of those attempts actually be good.
At this point i would just pay someone to do the challenge for me so i dont have to deal with it.
on another note we got Mythic Helya, and Mythic Augur down last night, yay progress.