Blues and Greens should never push Legendaries or Exotics out of the Postmaster
Simple enough, the postmaster should prioritize Legendaries and Exotics over any thing else. They should only get pushed out if the postmaster is full of nothing but Legendaries or Exotics. It's really easy to lose a legendary drop from the new raid right now if it went to the postmaster and you don;t leave the raid.