Cause let’s be honnest, that’s one of the very few weapon that’ll work on this difficulty
You want to farm the cathedral of the twin god, but take the back entrance : You fast travel to the great vault go back to the cathedral. There is an elevator in the lair of the skull smasher mini boss, then you reach the part with the saw blade.
There is a respawn machine, an amno machine, and lots of enemies with a good density of badass a bit before that. They seem to be blocked by an invisible wall that prevent them from going back to where the saw blades are, meaning you can farm here, and since its the area on Pandora which massively drop shotgun with the event, it’ll be fast.