Well, I've been playing a bit lately, and until yesterday I was using Autoswitch, so I was always fighting for the country with the fewest players.
I kept track of it a little, so I can tell you which side was outnumbered the most often:

Interestingly, Autoswitch doesn't really work very well anymore. As the numbers are way too low to allow for battles on every front, I often found myself kicked from the only battle on the map to a chesspiece without any activity at all on all of it's fronts. And not only the country ganged upon is not only not the one with the fewest players, but at low numbers times a country can have most players in arena but least number of active ones at the same time.
One example: I enter the arena, getting put on Knight side. But not a single player on any side is "inflight" at all. So I roll my tank to a Bish town and lazily keep shooting at buildings. After 15 minutes, suddenly some more Knights show up and join me in the perceived "capture attempt". Still no Bish reaction, and as I tower after having used up my HE rounds, I get autoswitched to - Rooks.
Over the next hour or so, I see 4 Knights capturing Bish base after base, against no resistance at all, while all I can do is watching the map from Rookland. I was even doing a 9k bombing run against Knight targets, but they just ignored me (smart from a strategic point of view).
I could have disengaged Autoswitch to manually jump to Bishops, but I would have stuck there for the next 6 hours, while after one hour the Bish would wake up and quickly totally outnumber both other sides combined.
While this is a more extreme example, similar was happening quite often even during US prime time. Two sides locked in battle, while the third either milkruns undefended bases or is not doing anything at all, with no red darbars to be seen anywhere.
I think it would be sensible to drastically reduce the time limit for switching sides again.