I understand Blizzard's reasoning for restricting legendary xmog, but what if they added some restrictions to ensure you don't see HoR and TF's everywhere.
Some ideas off the top of my head:
1. You need to be exalted with the rep from where the legendary comes from (ex. Hydraxian Waterlords for MC legendaries, etc.) Retracted
2. Add an unlock feature where you have to pay a certain amount of gold to be able to xmog legendaries - make it like 10,000 or 25,000g so it's not "easily" obtainable. As we saw with the Shattered Sun title, it's a gold sink for purely cosmetic reasons.
Legendaries are definitely easier to farm now, but they still take weeks (if not months) of farming and in some cases a few friends to farm raids with. I don't think they're necessarily easy to farm and take some dedication so I don't see why legendary xmogs should be limited forever.