"Bad" teams dont plan ahead, and always get together to do games at the last minute before maintenance/points rollover. So for the US realms, on monday afternoon/evening you will have a much larger pool of teams to face. "Casual" players also get a piece of gear tuesday morning... freak out and wanna use it right away, so sometimes tuesdays are also good right AFTER the rollover.

Best I can figure it. I know last monday night we got tons of teams playing... and just crushed people.