As someone that is now trying to collect all the pieces (originally it was to get higher light drops for infusion, but that is unrealistic) and having put in many hours since the April Update into running Heroic Strikes I feel that the drop rate of unique boss drops are incredibly low even with a Vanguard Streak active. There is a higher chance of getting an exotic with a 3oC than seeing a boss drop anything better than some blues and a legendary class item engram. The game has gradually become more rewarding in pretty much every activity you can do now and I think the logical next step would be getting these drops to happen more often, especially for strikes like The Undying Mind and Will of Crota which seem to have a much higher quitter rate than any other strike (especially the former which often takes up to 3x longer to complete than other strikes). Better yet, why not add a consumable item like the 3oC designed to increase the drop rate of unique strike boss drops (and perhaps on rare occasions double payout like 3oC)? I would pay Xur for some of those...