I absolutely appreciate the feedback. Nothing is more frustrating than wiping and not knowing why. Now we have some things to target for improvement, and that's much more doable. Thanks to those who responded.
For this fight, tell your healers to have relics and signet of stability. It breaks the stuns and keep them immune for a short time so they can still cure if you have a Seer up.
Freedom of Mind (T7 potions) also helps. Does not have to be grandmaster.
And of course, everyone in raid should have pots for self cure.
No it cannot. Only if it expires naturally on a player. Also note that pet classes do not have to back off their pets when they are cursed. Only the player has to stop.
Can Combustion be triggered by un-cured detrimentals on pets? How about on dumbfire pets?
My understanding is that combustion happens when the swarm of adds is not killed fast enough. I think you have 25 seconds to kill them once they've spawned.