They get comms the same way everyone does: they have to make an impression. Gameplay is one way, sure. But it is far easier to notice when a DPS screws up.

Easiest way to make an impression on me as DPS is attitude and choice of glamours. Things that help is looking the part of your chosen role and job, and greeting the party either through chat or emote. I admittedly do have a bias towards Midlander and Raen females.