Blocking based on GeoIP is not 100% accurate. I hear it is only 99% accurate on country level and 80% accurate within a 25 mile radius. Besides there are ways to evade such a ban with the use of a proxy site and there's plenty of those in Asia. Granted those things cost money, but I don't think it will make margins low enough to entirely prevent gold farming.
However I think it would surprise the WoW administration if all of the sudden IP's popped up that came from countries like I don't know North Korea for instance
