Your contribution matters a lot more than you think. As a healer main, I disagree completely with you. I have had numerous people comment on how much faster this or that dungeon went because either the entire group was good, or because I was able to keep everyone alive while the tank wall to wall pulled. I would maximize DPS between oGCD healing as well.
You can also make things go more smoothly if you communicate with others while being positively constructive. Some people just need a little guidance.