As usual, if I'm on DPS myself I generally commend my fellow dps if they are doing good dps and don't do something silly like ignore mechs or otherwise behave like a jerk. If they don't get it then it goes to either the tank or healer, same criteria. If I'm healer then I'll commend the tank first with the same criteria, followed by a DPS if the tank isn't up to standard. The most recent commend was while I was on dragoon and it went to the dancer in my Stone Vigil levelling roulette.