How about making it so legendary and exotic engrams only have a chance to turn in to gear for other classes, if you actually have those other classes made as characters. For instance, I only have time to play 1 character. Therefore I don't use my other two slots. Anything that drops for me should just be for the class that I play. Now say, if I had two classes, then only items for those two classes should be able to materialize from engrams, and so on and so forth. This would definitely help make the game feel like less of a grind...