It's simple math. You have a 10% CHANCE to get an engram. Of that CHANCE, maybe 10% is a legendary. So, you actually have less than a % of a chance to get a legendary. Maybe a 2% chance to get a rare. Farming that entire area and taking 10m to do so out of a 30m total mission, is actually wasting my time considering I have 2 guaranteed blue Engrams at the end of the strike... I really don't comprehend why that's such a hard concept to understand. It's chance vs. a guarantee...