Oh, mannoroth, I thought you meant archi. Can kind of, maybe, see it on Mannoroth. We had the same Dark Sim drama on prog. It was nice bonus damage if the imps weren't dying fast enough, but felt like log cheese, as if imps were getting casts off to dark sim then they were probably not dropping fast enough or being stunned. We usually mass grip then stun them and they don't cast. Just means the raid takes less damage I guess and dks don't look as good
I did try the mythic warforged class trinket on mythic arch last night. Only did 8% of my damage so swapped it out straight away.