Yeah, unfortunately the Depth pass is tied to the focal point, so you would have to render twice if you want to render DOF and a true depth map.
For depth what I do is set the focal point at the nearest object in the scene and then use only rear blur, setting the rear blur distance to the farthest object in the scene.
If you do need to render twice you can set up a depth render that should go pretty quickly, since it doesn’t require any lights, materials, or effects (like GI, AO, etc.).