You have a better change of hitting the lottery than getting the "Orpheus Rig"... swear I opened well over 100 exotic engrams. I have more Lucky Pants and Raspberries than I could ever use.
Is it true that if you keep the NightStalker equipped you are less likely to get the Rigs dropped? do engrams give you the opposite of what you keep equipped? I fucking hate pulse rifles and its all I ever get!
What you get is completely random. Although for exotics, i've noticed you are more likely to get something you already have than getting something new. Your best bet is XUR to complete your exotic list
It's completely random. I did get about a dozen graviton forfeits and a couple dozen aoen swifts before I got my last exotic weapon tho. Xur's special engram is ur best bet.