Ya know i thought of the same type thing when i was doing the regicide mission and popped on a 3oc before oryx. It used up the buff but nothing dropped... Made me wonder if there were special exotics that drop off the heroic daily bosses. Theres so many exotics not accounted for and they stated they want you to go get them doing stuff. Wonder if thats why 3oc is like it is and you can grind out heroic dailies in hopes for the rare exotic. Just some thoughts