Also, I think its very very important to clarify something. While 20 people will get things faster, you need to also consider the return on the investment of each item, and how it is magnified by a group.

A stone wall has the same cost no matter the group size, but each person in the group benefits equally from that wall. Therefore, the larger the group, the more valuable that stone wall is. The return on the investment of mining a node actually increases with group size, not to mention that the actual act of mining is easier.

If the return on an investment is player specific, and the benefits are not easily shared across the entire group, then the return on the investment actually decreases as the group size increases. This is effectively a natural nerf on zergs, which are undeniably overpowered.

So yes, while a group of 20 might get research paper (in my suggestion) faster than a group of 2, the effectiveness of that research paper will be lower per person, providing a much needed group size power nerf.