Most of the "blur" seems to be along the vertical axis, while the horizontal axis is relatively sharp. This leads me to suspect motion blur.
I would try again, make sure the tripod is really solid (if it has a hook, hang a weight, or use a sandbag or something, also, avoid anything that might induce vibration such as walking around during exposures etc)
Use mirror lock up again, and use the 2 second timer or a remote release, make a test using live view focusing, try again. If there is no improvement, the lens is probably a bad copy