Seems like a powerful raiding rune to combine with a full backstab build, but I don’t get what you’re meant to use for the other 2 rune slots? Deadly brew is on the same slot as Slaughter, so Envenom seems mostly useless on its own… And Between the Eyes and Blade Dance are also mostly pointless for BFD. And the glove slot runes are all just primary abilities which are all pointless because your primary ability is already Backstab… And why would you take Shadowstrike when you already have a discounted Ambush? Seems like every single rune is pointless when you’re already running Slaughter from the Shadows.
Also, I did a full BFD clear with Mutilate spec yesterday and it felt like my Backstab hits harder than Mutilate. I suppose there are other factors to consider such as Mutilate generating more combo points per energy spent and Mutilate having double the chance to apply poisons - but if not for the fact that SftS has no other rune synergies, I feel like a Backstab build would out-dps the Mutilate build in a raid scenario where you can always be behind the target?