Did 5 speed runs yesterday and on the 4th upon defeating the boss I got the last word. You do get engrams along the way but I usually only get 1 blue engram along the way and then 2-4 upon completion of the raid so in my opinion it's better to speed run it for the roll at the end. The extra time spent to pick everyone off along the way isn't worth it for 1 blue and a few green engrams. Of course maybe I'm just unlucky with the blue drops. After those 5 strikes I turned in about 18 rare engrams and 1 turned out to be legendary.