Blizzard Silently Nerfed Dual-Wield Killing Machine Proc Rate in Shadowlands

Just because you had the ability to, doesnt mean that it was. You have the ability to eat a steak with a spoon, it doesnt make it the right choice.

It was only good, because of a bug, where Sudden Doom was proccing off of the offhand which wasnt intended. Otherwise your damage was in the gutter.