Scott, it is not even the double team. Although the double team is ALSO a result of the ORGANIZED 3rd chess piece. It goes like this. One team swoops in and gains an early advantage (amplified by strat downtimes) and begins working the base capture. The easy target (ie. chess piece with least players or the base with the least effort to take like ports) is top on the "WIN" team's agenda. Success of the chess piece gains momentum and players stay logged in longer.
On the flip side, as you experienced, once your entire team is delegated to defend or even worse don't care (the majority at least say so) frustration sets in and players log off, or sometimes even preferring to join one of the aggressive chess piece teams. If you stick it out, seeking the fights that you signed up for, you begin to explore the other chess piece's defenses, good of all concerned to be dammed. There you go, a double team.
I warned of this back in beta, only not as detailed as now. I saw certain individuals sharpening their base grab intelligence and picking up on any faults of the map design meant to balance chess pieces.
To keep on topic, Buzzsaw is a wonderfully planned map. It reminds me of Grinder, in that it was popular but never survived for long. The problem that I perceive is the way the 3 chess piece system rewards the chess piece that is better at acquiring and maintaining superior numbers.