Started doing these runs today with druid/priest/mage/warlock/warlock (although I am just lvl 30 so starting out in RFK).

Threat is not really an issue other than that it reduces the size of pull I could do (pull needs to be small enough to be able to heal my druid while it uses 6+ Demoralizing Roar before I start aoe and not run out of mana).
Probably going to try to upgrade my gear before I go into SM for more mana on priest and more hp on druid.

Biggest issue I noticed is Eye of Kilrogg, sometimes it takes 3 seconds for it to get aggro and sometimes it gets aggro instantly. Sometimes it gets aggro from a distance and sometimes it needs to stand on top of the mob for 3 seconds. Because of how unreliable the aggro is I sometimes get tiny pulls (5-6 mobs) because they get a lot of attacks in and breaks the Power Word: Shield.

Another issue I had with Eye of Kilrogg is that in one pull the mobs reset after the eye died (probably because I went so far away with it).

Currently I am getting ~18k xp per hour, kinda low for AoE (although it is a lot lower in reality because of all the mistakes I do and all the breaks I have to take because it is a lot more tiring than grinding non elites or questing).