Failteams make me sad. It's only possibly your fault if you are one of the top tanks. You are required to disable their equivalents on the enemy team. If you find yourself in a mid-lower tier tank and are completely swamped its probably because your team did something wrong.
Generally what I see is clumping on one side, flat out ignoring one side and losing the cap.
Diffuse deployment, they all scatter to fuck or the faster tanks don't wait for the bigger guys for support.