If you're gonna go for a strike specific reward and do that strike only for that purpose, you will end up disappointed. If you don't expect it, you will end up happy. Something you may not want to hear, I know, but just an advice: Forget about them, do other activities, one day they might drop for you without expecting it and you'll be happy. If you keep grinding one strike for that one specific reward, you will end up upset and disappointed each time you finish the strike. I got machine gun from Steroid-Shank, Auto Rifle from Taniks the Scared (yes, scared, fleeing coward) and Flayer Cloak from..flayer. Didn't farm any of these and was well surprised and happy when they dropped. Everybody loves RNG!