They drop pretty rarely, possibly as rare as GSoA.
They drop WAY more frequent than GSoA. I can see them being used for UCv1 (not V2).....at least that way they would be useful and not just taking up room in my bak slots.....I don't know why I waste my time looting/saving these...I guess in hopes that one day they be useful....if not maybe just take them out of the game all together.