Martin, dithering is especially useful for a DSLR with unregulated cooling. Cooled cameras can be calibrated with darks.
If you're guiding isn't great, then work on the mechanical issue(s) in the first instance. All dithering does is issue commands to the mount to move a small amount in a given direction, in the same way that the guiding software does. Improve the mechanical issue(s) and it's win-win
