My first priority as a healer is to keep my party alive. However just healing puts me to sleep especially when farming tomes in the same two dungeons for the week.
I treat every group the same. I'll heal, I'll dps.
The second I see dps eating aoes or tanks who won't pop cds on big pulls.. You best believe I am going to turn my cleric off and go straight to healing only.
I refuse to put out my best if the rest of my party isn't.
Now if a player or two is putting out effort then I will as well but I refuse to be doing all the work in a party.