Since you’re curious, I recorded a short video demonstration. For it, I took away their legendary bows, and gave them all dragonbone w/ adv. damage kits. Being as I’m also a PvE player, I’m quite aware of how long it takes so get a top-tier thrall to max level. So for this, 4 of the RHTS are level 0, and one is level 5 because that’s what was already there.
Since someone had just used it to kill the boss a few minutes prior, I (being too impatient to wait since it was my lunch break) simply spawned a new one. Combat started at 0:56, ended at 3:32, so about 2.5 minutes. Generally it’s faster for me since I give them legendary bows and help out with the fighting, but you get the idea.
Point is, a minimal setup allows a player to use brains (rather than brawn) to defeat a PvE challenge so as to acquire better loot for taking on harder challenges.
EDIT: FWIW, retested w/ their legendary +Accuracy bows equipped, and that dropped the kill time to 2 minutes even.