I've been using mining the past several weeks and been making huge amounts of gold. I'd recommend if your looking for fast gold and you have mining near 540, I 'd say go to Pandaria and start farming b/c who knows when blizzard will hot fix the vein node spawn timers.
I've managed to get over 400 Ghost Iron ores in 30 mins or less. I usually do my farming in the northeastern part of the Jade Forest. Its a small island out there, Ores spawn rapidly too.