We will update the development server with a new distance based rate decrease algorithm soon which is based on the pairwise union of spheres as I described above. The algorithm will behave like this:
If two RGS are built in the very same spot, the total generation rate will be as high as the rate of a single RGS. If three RGS are built in the same spot, the total rate would drop to 3/4 of the rate of a single RGS. For n > 0 RGS with identical origin the total rate would be n/2n-1. So building two RGS close won't give you any strong advantage or disadvantage (besides the redundancy if one of the RGS gets destroyed), but cluttering your base with many RGS will still let the generation go to zero. For that reason, RGS can also be used as a weapon against camping. If your enemys don't leave their base, you can build a number of RGS outside of it to deny their resource generation.
If a number of RGS are built so that the ideal distance is only slightly undershot, the algorithm won't penalize you anymore. All RGS will generate at nearly 100% efficiency.
You will also be able to see the efficiency in the health bar of a RGS if you build your client from the resources branch.