I can somewhat understand where the feelings are coming from. As a healer, you play to heal. It feels good to know the party survived through your efforts. I've recently come to realize this in a similar manner. As a tank running through old content, I don't feel useful or have a satisfying experience when the party doesn't allow me to do my job as a tank. I came to absorb damage and keep enmity, not so i can watch a ranged dps sprint ahead and run circles and around enemies as a makeshift tank.

The point being, we choose a class to play because we want to fill that role. If the situation arises where help is needed then by all means. I just don't think it's doing anyone a favor or lending to their enjoyment by taking the opportunities from them.