First: So you're admitting that tank and heals dont get them because they're performing very good but because they're more needed - so to repeat again to you: Commendations arent judging your performance so much but an overall appereance.
I would guess that I got 50% of my commendations simply because I was the tank, 25% because of my looks and 25% because I was chatting and making the run more pleasent for everyone.
Second: Full-group dungeons shouldnt count then either, right? Because you cant get a commendation at the end. (And really, you should get rid of those horrible, horrible friends making you run dungeons with them - how... insenstive of them!)
Third: And please, please explain this finally: Why do you believe this weird "ratio" of yours should be 1:1? That is sololey based on the assumption that you'll get (or deserve) one commendation each run you're doing - so out of seven people in a trial you're playing good enough to impress one but not the other six... I'd say this 1:6 commendation ratio there should tell you: Way to go, buddy!
Upholding this weird idea of a 1:1 ratio is only going to make you unhappy about a topic no one really cares about - personally I dont tie commendations to duties that strictly. But I also view my commendations as a "Thank you for being a pleasent companion" and not as "You did well in this run" - I got 3.600 "Thank yous"; I didnt do 3.600 good runs. THAT is the value of commendations - the amount of people who enjoyed playing with you, for whatever reason. Simply your job (because they were so happy they got a tank after waiting for 30 minutes that they didnt care about the performance anymore), your glamour, your jokes, your explantions, and maybe, once in a while, your performance. Commendations arent school-grades a teacher gives you - they're the little notes and hugs from your classmates saying "Thanks!"