It's tanks.

Yoshida actually made an announcement stating tanks are the least played of all classes, and would like to see more people play tanks. However, I do and do not agree with him wanting to see more tanks.

On the agreement side, It would be nice to see the queue times in the duty finder drop for everyone, so that no has to wait for very long.
On the non agreement side, and this is coming from a person that normally plays tank/support classes, I would rather see a low number tanks in this game, being played by mostly skilled players, then a high number of tanks, being populated mostly by bad tanks.