After doing a little research today i noticed that obtaining the Elite PVP set in Legion require a lot of luck, not also skills. From what i'm reading we need to be extremely lucky to get the elite set parts, one by one dropped from the weekly boxes. Some people might never manage to get the whole set if they are unlucky.
Think it will be better if they add an extra way of getting it via NPC selling the transmog look (like in MoP/WOD) once we reach 2000 rating and Prestige level 4.