Well, the game rewards blind alignment choices, based only on the alignment, and not in the content of the choice itself.
Why would I choose anything but Full Dark or Full Light, if the rewards for getting it are almost demanded for endgame (and even leveling)?
After getting endgame gear, you can just ignore your alignment, since sets don't have alignment restriction and you'll get better relics through it.
Right now, I feel obligated to go Full Dark/Light up to the point where I can get endgame PvE or PvP relics.