I hope all bungie does to engram's is make the purples that turn blue show as blue when picked up.
Getting all purps through marks is already brain dead easy, and shouldn't be superceded by running around in circles in some shitty farming scenario.
people wanna play dat lottery game though. You could easily get full Legendary gear through marks in less than 2 weeks if you are smart about it and level crucible and a faction. Hit the mark cap just by playing the game like you should and sometimes you get lucky along the way.