I know that allot of people have this problem, but I am going to report it in detail.
When I use my recommended settings( minus post-processes and anti-aliasing.) I get about 20-40 average fps during most of the showcase missions. In the editor( empty) I get 40-60 fps. In MP no matter what my settings are i can never get above 40 fps.
To combat some of this, I have changed my settings to low overall( textures, objects, and particles are standard. Shadows, Vsync, PIP, and clouds are disabled. HDR is on low.) The view distance is 1600, Object draw is at 1105, and shadows are at 100. After doing this my performance hasn't changed much in SP( showcases), but in the editor I get 50- 90 fps when empty. MP is still unplayable at below 40 fps.