well Ive had Gjallarhorn since the end of week 1 (seriously) so i can say ive definitely gotten my use out of it. However whilst making various exotics redundant is completely stupid i believe the only reason they have done this is because they just were constantly failing at getting a balance in weapons. They introduced etheric light only to ditch it again because they cant balance legendaries. In the end it has been easier for them to render most weapons useless and to start a fresh with weapon balancing.