It was never made clear exactly how the sets would work, and there was a lot of discussion on whether or not the 71 vanity helm would replace the cop in the set. I don't recall a clear position from STS on what exactly would be happening.
During the build up to Humania there was a fair amount of advertisement and emphasis put towards players getting the elite vanity. There were elixer sales and even a platinum sale in the months prior to the release. Now I'd be willing to bet that the PL player base increased substantially between nuri and fang, and even more so between fang and humania with the (8 month?) endless wait.
For every player who began playing during mt fang there was absoloutley no reason to believe that once they grinded their way to 66, after countless elixers thrown out the door, all that work would be for absoloutley nothing. Even for the players who have been playing since the Nuri campaign, it was never made clear that unless you started playing 6 months earlier you'll never get a full set. Even now the level 71 vanity is useless to everyone until the next campaign comes out; and who knows when that's going to be?
So essentially mt fang armor on its own is a 300+ platinum piece of vanity armor with no stats, even when combined with another 300+ platinum vanity helmet both are nothing but eye candy, and I use that term lightly.
I can't think of a universally friendly way to fix this issue, but until something is done I wont bother going for 71, which is a shame because I now have a whole lot of useless platinum.