Hmmmm..... that reminds me of how some of the early speculation was that the Elachi had varying mob sizes/qualities and that some people's problems were that they had more enemies to deal with than others did. I'm not sure if it's true, but it seems plausible.
Now your tempting me to go back on tribble and run it a third time to varify this. After last nights run through this theory seems quite plausable. One of the other experiences i had last night as well was the Elachi capital ships moving off to their own space away from the support vessels and remainder of their fleet.. At one point, I had to fly around a third of the map trying to find them..