Realistically, this could fall under an entire category of adjustments for past content.
Has the dev team considered adjusting the CoP wyrms (Tiamat, Jorm, Vrtra)? I'm surprised nothing was done when the Black Belt HNMs were adjusted. The unpredictability of a three to five day spawn window did offer these monsters some mystique, at least until it became the norm to have a mule dedicated to camping the spot (well, only for Tiamat really). Similar to Abyssea VNMs, this seems to be one of those things that remains inaccessible due to competition no matter how low the world population seems to drop.
It would be less of a gripe if Tiamat didn't drop Herald's Gaiters; which, if I'm not mistaken, are STILL the only 12% movement speed option for some jobs. The disparity in challenge for acquiring movement speed items has always been baffling anyway, especially in a group-focused game. You have this item that offers nothing more than what a number of other items do for different jobs; and yet it's an uncommon drop from a HNM that rarely spawns and is mostly dominated by a tiny minority of players who are willing to dedicate a character just to camp it. On top of that, this tiny minority always has a gil incentive, so the situation never changes.
Hopefully GEO AF sets a precedent for upcoming adjustments and they'll toss 12% movement at all of us.