Earlier I found four in ten Tiger strikes. 2 were end of match rewards. Try this as it's what I did: max out vanguard marks. Equip appropriate glimmer booster. Do work. Head shots seem better. And cross your fingers. Run stokes consecutively(didn't get any engrams until after my 3rd stoke in a row. Don't leave the queue. Just keep doing them until your inventory is full. It may not help but I've never gotten anywhere near as many legendary engrams in that time span. Good luck!