I had this exact same problem. My specs are a FX 8150, 8gb ddr3, and a r9 280x power color. I figured this would be great for gaming, but on BF4 I averaged like 40fps?!?! Not what charts shown. But I found the solution, its acutually isnt the GPU, its the CPU. The fix is EXTREMELY easy. Just go into your BIOS->Overclocking->CPU->CPU Features->HPC, and turn HPC ON. HPC will stop the processor from underclocking itself under easy loads. So when you go into a area of a Bf4 map and there are few people, it will underclock thinking it doesnt need to work, in turn giving you minimal performance. Hope this helps!