This is a response to a thread that was locked.

Q: We expect that The Elder Scrolls Online offers support for DX9 (again the good range of machines) and maybe for DX11 too? If not why do you stick to the DX9-API?

A: On Windows Vista and Windows 7, ESO runs with a DirectX 11 renderer, but we do still support Windows XP and DirectX 9.0c (shader model 3). We wanted players on launch day to get the big performance boosts and improved effects with DX11, but it is also important to let as many people experience the world as possible.

Source:http://www.pcgameshardware.com/aid,1034123/The-Elder-Scrolls-Online-Improved-effects-with-DirectX-11-Exclusive-Tech-Interview/News/

Also at PAX east the game was running for some in DX9 and in DX11

Thanks for that info.