Long ago, I was afraid of "important" roles because, oh god, what if I screw up???

Later I learned most roles require some degree of skill sooner or later, and the "hard" classes were actually not that hard at all. Being a bad healer was easier than being a bad rogue.

More importantly,  there's no warrant the other player would be up to par, or even trying to be there. He may be a bear tank wearing cloth because he thinks it gives him better dps.

Now I just play what I want the way I want because chances are whoever is on the other side is doing the same. Be it a venerable paladin or a troll-healer meleeing the boss.

Also, play with friends. It solves most of the problems.