Hey all i have been having FPS issues with ESO since the beginning and up until now have thought it was a problem with the client. I have spent hours and hours on google looking for fixes to my fps problems but nothing i tried worked until i launched CPU-Z and found out that my CPU was spiking.
From what i have discovered, the main problem especially to AMD users is that power saving contingencies built into BIOS and or windows that can seriously cause your CPU to spike.
1 - You can try unparking your cores. You can do this by downloading UnparkCPU (Google it as im too lazy to link :P)
2 - If that does not work then you need to go into bios and find power saving function for your CPU, For Asus/Asrock the option is called Cool and Quiet and it is located in your CPU section of the bios. (I am unsure of the other Motherboards name of the function but it should stand out) Basically this function with stop your CPU from going into idle and keep peak speeds at all times (BEWARE this can cook your mobo/cpu if you are overclocked and or have insufficient airflow in your case)
3 - IF YOU HAVE A AMD BULLDOZER CPU DOWNLOAD THIS HOTFIX FROM MICROSOFT (Optimizes scheduling for tasks to be shared across all cores) -
http://support.microsoft.com/kb/2645594
Hopefully one of these fixes will help you out like it did me.