Easy farm boss nuker weapon?

Hey all!

Obviously the BOD is a great weapon, but I'm having a hell of a time farming it and my best weapon right now is hot Slugger which isn't all that great for some bosses on crit Rafa. It makes reasonably quick work of them, but honestly my purple smg with taser is faster.

Any ideas on an easier gun to get to drop for quick boss takedown? Is Oscar Mike or Complex Root an easier drop than the BOD for instance? Anything else that's quickish to farm and melts them?