I've been spamming Tiger Strikes for the past couple of days and I get a steady stream of blue engrams/items each run (1-2 engram pickups, 2 as rewards at the end or an item and an engram). It takes about a half hour with a decent trio so you're looking at 6-8 blues per hour roughly. I've still never seen a legendary engram drop. My only legendary item is an Unfriendly Giant rocket launcher I was lucky enough to get from a blue engram. All the rest of my weapons and armor are blue rares and I'm stuck at Lvl.24. Bungie really needs to make legendaries more common with you're mid-endgame (23-24) because Lvl.24 is a major bottleneck right now. I mostly play solo so I can't attempt Nightfalls or the harder strikes since there is no matchmaking and Tiger Strikes are easy but don't reward well enough. All I've gotten for my trouble grinding these is a couple of strange coins, a level or two with the Cryptroll, and a ton of blue weapons and armor dismantled.