These arent the same as mike rainbird sells, mikes are very thin toe shims that toe the rear wheels in slightly. This improves tyre wear and gives the rear a more centred feel.
The camber shims may be better than nothing, but not comparable to a six degree beam. They dont correct the toe changes under compression and extension, causing instability under braking etc.
Granted there is a big difference in price though...
Diff mount is also a good investment to improve handling