I don't know if its this way just for the beta but bosses or mini bosses need loot drops. I killed about 15-20 devil walkers and the same amount of the giant orbs in the devils lair and not once did I get a loot drop besides a banner every now and then. But banners are only worth 200 glimmer and I get get almost that amount from one chest and I could find about 10 of those in the time it takes to kill a boss. There needs to be loot drops or some sort of better pay out for killing bosses other wise whats the point in spending all that time to kill them ? If anyone knows different please let me know. If not bungie please fix and add better loot drops for boss type enemies. This is my only major complaint other than this I love this game and cant wait for its release.
OR...you could just enjoy the challenge and the guaranteed uncommon you get at the end of the strike. The game isn't designed to inundate you with loot for every moderate exertion, you may want to reduce your expectations.