Anyway, I will retract my position on there necessarily being a good way to farm it. Apparently, the first person to get it was lucky enough to get a Puzzle Ring (thanks loot 2.0!) and he duped it for the other 3 people who have the achievement (thanks offline!).
Then how do players get this hours after completing Inferno for the first time (and spending less than a day in Inferno total)? They must be doing something. I know there's no guaranteed spawns...but there must be something more than "just play the game."
I just finished Normal, and I killed over 20 goblins (got the achiev in Act 3). 4 difficulties = 80 goblins. Couple hours later = 100?
I don't think I have even 9 hours played. Do the math?
If you play the game you will get your achievement. Then you can go trade it in and buy another game to get achievement points. Then eventually when you realise achievement points mean nothing you can go get a job.
I said they added it to the console game - that does not imply that it was not in the PC version.
Actually, yes it does as the console version is a port of the PC version. Added would refer to an addition of something that wasn't there before, or would you descibe all 5 classes and all 4 acts as 'added' to the console version?
Examples of stuff that was actually added:
Farming specifically for Goblins is an extremely inefficient use of time, especially if you want other achievements. It will just occur naturally and much quicker than you expect.
Also, there is no single location that spawns more treasure goblins in general but you can maximize your chances by doing runs as fast as possible. This means to spec 100% for speedfarming and farm on whatever difficulty you one hit monsters. If you can rush through enough areas fast enough then you will maximize your chances at seeing more goblins/time. As for which routes, I'd suggest high density areas;
Act 2- VotA
Act 3- KD2
But as I said initially, you're best to let it come naturally, or cross your fingers for a Puzzle Ring. In the time you can target farm half a dozen other achievements, you will get this one naturally.