The two graphics options that should have the biggest positive effect on FPS are changing resolution to 1280 x 720 (or higher depending on your hardware configuration), and lowering the Shadows and Texture Quality settings from High to Medium or Low (again depending on your hardware configuration). These can have a substantial impact to frame rate, but can also significantly reduce the visual quality of the experience.

Note: You should restart the game client after changing video settings.

If the frame rate is still unacceptable after making those changes, please send your DxDiag.txt via the "Click here for help" link on the bottom right, and we'll take a closer look and your configuration and recommend further changes.