As a tank main:
1: Co tank without any hesitation. I understand the struggle. If you're my buddy, you get my comm no matter how good the other players were UNLESS you were utter shit, had a terrible attitude (someone told me to "get it together" in 012s when I hardly made any mistakes, lol.)
2: Baller healer that kept things going or saved a wipe. My great friend is a healer main and a GOD LIKE healer. You remind me of him? Comm, if the tank was average.
3: The other two were derps? DPS that did the most. ESPECIALLY melee.

Usually in 24 mans it's:
Healers that stabilized a wipe
DPS that USED THE LB properly and did fantastic dps.
I can't usually comm a tank because I am the tank, but if I'm on something else, I'll hardly ever give it to the tank because they don't really do anything.

In 4 mans:
Healer for keeping me alive
They let me die when I know I did everything properly? DPS that did the most