Very much spec dependent. Out of all five challenges, each spec handled them to various degrees, some challenges weren’t difficult for some specs while others still struggled.
Outlaw required reliable group burst damage for its challenge where it’s strength was reliable group sustained damage at the time. It was one of the few times Kil’Jaedins Burning Wish was actually valuable, but the cooldown was still longer than it’s need.
The only way I passed that one even being outgeared was a convenient bug that happened halfway through the expansion where the boss would spawn on the opposite sides of her minions, so that they would have to run across the map to join her every time, giving plenty of time to cleave them down before they reached her.
Subtlety was also difficult in the second half when needing to burn the ads down before they healed the boss, more than damage it was execution of slows and stuns on a group of enemies that was more important. Most walkthroughs acknowledged even with gear, Sub wasn’t going to be able to take them all out before they found the boss, so it would be important to kit a millimeter at a time and make use of the most space to try to burn through the healing the boss got.