After posting my review last night of the two trades I read recently, I did some online research to answer the questions I posed regarding the contributing artists and the duration of their contributions.
As far as I can guess, Byrne was slated to be on The All-New Atom for six issues and likely left due to creative conflicts. Everyone knows that Byrne has had some rocky assignments and lacking a better explanation, I will assume Eddy Barrows was brought in to pick up the slack when Byrne exited a little early.
Also, the Atom series concluded with issue #25, so even if I did like it immensely, I wouldn't be finding it on the shelves of my LCS.
With Pacheco on Green Lantern, if issue seven was included in the collection I would have realized that he and alternate artist Ethan van Sciver traded off art chores every three issues to accomodate the monthly schedule.
This one, perhaps, may require further exploration. Any comments or opinions regarding the series post "No Fear" would be appreciated.