That's the nature of the game. There is always something that is best, and it's not going to be a green at level 50. Right now, absolute best in slot is a custom piece that has been crit-crafted to have an Augment slot. In the future, you'll be able to add Augment slots to existing pieces, which will create much more opportunity for BiS gear. Which is pretty much what we want so that there are a wide range of options for people in terms of endgame aesthetics.
Ah, that looks reasonable. Did not know they were planning on implementing that.