Best farming for what, gold I'm assuming? For me grinding on WoD mats is the most profitable, with a chance at BoE's which are like 10-20k.
maybe if you were a little more specific in your request. to semi-quote a forum mod 'if you only spend 10 seconds creating a post, don't expect anyone to spend more than 10 seconds on a reply'
the term 'grind' could mean any repetitive task that yields a sellable item, or just plain expee. often i grind Arcane Crystals. ive got a profile that runs a circle somewhere in Azeroth gathering Thorium ore and Arcane Crystals. i just vendor everything but the crystals. They sell for a decent price, but limited supply keeps it that way.