I only give Comms if someone is playing well. And that only happens 50% of the time. And when it does & more than 1 person is doing well I give to Tank/Healer if I am Tank/Healer and DPS if I am DPS. I don't need a parser to know how good someone is as I play every job exceedingly well...coughbragcough.

Most of my comms were from levelling tanks/healers, though I usually get 1 as a DPS. Mostly as a MNK, I've gotten 4-5 a few times?? I weirdly used to take not getting comms personally but now that I have the dumb 3000 mount I don't even care anymore...