Sucks bro. It always seems to work for me. Dropped Devouring maw and and that LMG (barons whatever) one from special strike for the sleeper and one from nightfall. Got a flyer mantle from the nightfall this week and my friend that i ran all 3 on got two. (I got mine the one time he didn't drop one.) Darkblade helm and fusion rifle both dropped for me that way as well. (Helm from the nightfall, fusion from exotic sword quest. Sorry again it hasn't been working that way for you :(.