I Don't think its your system, many people including myself who run much much higher GPU's and spend 3x what you do on Rigs are having problems. The client change from P3-P4 Introduced some graphics issues such as micro stutter and drops in FPS with single GPUs.
AMD Released 13.8 Beta 2 Drivers to boost performance a little bit but it needs further optimization. The culprit is the change in clients thats causing issues on both AMD and NVIDIA GPU's.
SE in their infinite wisdom and foresight(Insert joke from EA Here) Decided on three seperate client versions from Alpha to Beta to Launch each one had their own issues Beta 3 being the most stable.