Clarification on Minigun 40% damage buff

OK. Bang Bang is bugged and doesn't get an extra damage buff from your awesome level :-(
Which on paper makes minigun look very good by comparison but is it really worth using minigun instead?

In another thread on minigun

@DoctorWagner said:
Removing the 40% tag to bosses made minigun worthless.

Was Doc referring to the 40% from the 20 damage stacks not applying to bosses (which would make minigun completely worthless imo) or to some other intrinsic 40% damage buff that used to apply but doesn't anymore?

Thanks