It wasn't a stealth nerf. It was a bug fix to make the goblin racial function as stated. This is the racial description:
"Always receive the best possible gold discount, regardless of faction."
What this means is you will get the exalted discount from faction vendors regardless of your standing with that faction. There was a bug, however, which allowed the discount to go beyond the maximum (exalted) discount provided to all other races.
We fixed the bug so that the goblin racial now functions as advertised. If you're friendly with, say Kirin Tor, you will receive the same discount as a tauren would who is exalted with that faction. If you're both exalted, you'll still receive the same discount.
Did a stealth nerf happen to this racial? I'm in the process of transferring a toon, and have too much gold to transfer, so I was investing some into the Vial of the Sands mount. As of two days ago, the vendor mats on my goblin, in a level 25 guild, was 2100g for the dust (20% best deals anywhere, + 10% guild level 24 perk) and 3500g for the vial. Now they're 2700g and 4500g, respectively.
What is going on here?