There will always be exploits of some type ... the more sophisticated the game the more complex the code. Test servers or open beta with character wipes still won't prevent exploits. This is because dishonest "testers"seek out and make notes of the exploits they find for their own use and never report them. Sometimes it…
Ban the exploiters or at the minimum confiscate all the exploited stuff from their accounts. Those who didn't exploit get benefits from the temporary flush to the economy (some cheap purples on the AH) and the exploiters are punished. Problem solved ... Next.