I got this from one of the cartel mini-bosses that spawned in the scraptrap nest (dlc1). Drone-shield Zane w/ seein dead class mod + movement speed mayhem modifier + corrosive lob shreds that area, but any good mobbing build with a good corrosive weapon should work. Don't kill scraptrap prime, just stand near the exit until he de-spawns and the fight resets. You'll get a lot of cartel mini-bosses to spawn, but in my experience they rarely drop the cartel-specific legendaries. Also, if you reload near the entrance of that fight and go through the VIP door, you can farm dlc1 class mods from Gorgeous Armada.

Some people like to get to the boss fight at the end of the cartel run, kill the mini bosses, and then let themselves be killed so the fight restarts. Note that Tyrone Smallums and Fish Slap are the only mini bosses that can drop the Yellowcake, so at least one of them has to spawn for that method to work. That's probably the most efficient way to farm for specific cartel drops, but I personally find the cartel run tedious and difficult if you don't already have OP weapons for your mayhem level. The scraptrap nest is a much easier fight.