Exploding rounds tends to mess with the firefly and outlaw perks. Single point sling doesn't do much for me as I tend to mostly run primary. And field scout adds only one round to the mag while carrying extra in reserve that don't really matter because primary ammo drops like it's nobodys business. Firefly also exists outside of Fatebringer while White Nail is a Black Hammer exclusive. I could run a scout with firefly and similar perks and it would be just as good with increased range. The only real comparison to Black Hammer is Bad Juju. I don't feel as though a legendary should be comparable with an exotic.