There's a side quest on Tatooine that funnels rep/imp together into a final plex. I think I spent more time finishing the side quest than I did the storyline. I was ganked a bunch of times (running solo) but I managed some sweet fights with other scrubs. I do wish I could see my stats now that I've managed to kill a few reps.
Maybe Daragon Trail is the odd man out but there seemed to be plenty of republic players on Tat. I'd say they slightly outnumbered the imps running through that plex.