Unfortunately, damage-dealers get the shaft when it comes to commendations. Everyone wants to reward the tanks and healers. As a healer, I tend to send one to that awesome DPS that carried the group pretty hard and did their job appropriately. There's always the doofus DPS who decides to pop-cooldowns early and threat is ape-shit crazy, resulting in them NOT getting my vote.

Seriously, reward your DPS once in a while. I feel bad for them. I heal all the time and get commendations for it, and so does your tank with his insta-queue.