The dungeon journal states:
"Final Harvest :
Amarth harvests the bodies of his minions, destroying them.
If the minion still stands, it explodes and inflicts 8,852 damage to all players. Otherwise its corpse explodes, inflicting 8,852 damage only to players within 8 yards."
Apparently if the minions are CC’d, when Amarth does Final Harvest, they do not explode and do damage all players.
I would argue that a CC’d mob is still standing. If not, the dungeon journal should be updated to reflect that.
It is issues like this that lead to toxicity in the game as you have those that are playing the game according to the dungeon journal and have others getting piss off due to them not knowing to take advantage of bugs in your game.