I'm a healer main approaching 3,000 comms, but I've leveled a number of tanks/DPS classes. At cap, I like to do my roulettes on BRD for a change of pace. I notice that I get quite a few comms on BRD, likely because I try to keep Foe's Requiem up as much as possible for caster/healer DPS and use swiftsong whenever combat ends. Regardless of which class I play, I try to keep an eye on the DPS players and if they're performing well, using their utility skills and cooldowns regularly, I'll throw the comm their way, since I feel DPS rarely get rewarded for good play.

Of course, some people give out comms randomly, or comm somebody with a nice glamour/name, or just someone who was personable and chatted throughout the run. It isn't always about performance.