Blizzard designed WoW to be a farmers heaven

Why else the auction house?

Just make all decent items BOE. That would effectively cut out many of the farmers. Separate crafting from gathering allow one craft and unlimited gathering trades to kill the rest. Restricting accounts to specific regions would put a stop to the power leveling.

Easily done with little impact to honest players.

Oh and stop allowing gold transfers through the in-game mail system.

Would Bliz do this? Just ask yourself how much money they would lose when the farmers dropped their subs........