Guys this is a PSA. Use the TOC's one at a time. The stackable buff occurs after the first TOC doesn't drop anything. It simply means that the next TOC will have a higher chance to drop an exotic. I have seen people all over the forums having mixed results using 5-15 coins at the same time getting drops at what seems to be the same rate as if you had used one. If you need an easy way to get these done then do the "scourge of winter" mission on Venus, not the strike "winter's run" (although this boss would work as well but you have to redo the entire strike). After killing Draksis collect what he drops and then go to orbit before the mission countdown finishes. This will give you the checkpoint for Draksis and the you can just kill him over and over again. Just remember to ghost out every time. Dying does not appear to effect the buff.