With the addition of Engrams as rewards, you're now 100% incorrect. Statistically speaking, IE if you actually do the math, you get more engrams from the mission reward than if you kill everything. Case in point, yesterday I got 12 engrams (Not counting Greens). Did 4 strikes. Had 1 blue engram drop in the strike. The rest were rewards. Had a total of 37 engrams. 15 green. 10 blue. 2 purple. 2 legendary engrams were rewards. 9 blue were rewards. 15 green dropped in the mission. 1 blue dropped in the mission. If you want to farm for greens, do it on your own time.