When I was leveling my WHM, I ran into two ACNs who loves to help out healing.

To be honest, in both cases I was at first slightly offended and then just wrote them off as newbies. During leveling content, especially at lower levels, one heal usually can fill 50% of the tank's HP. On top of that, only a few particular mobs have burst damage so it's extremely easy to predict incoming damage and heal efficiently, so I stance dance and heal to minimize overhealing while not letting the tank drop below 50% (unless the tank is extremely undergeared, then it's another story). But these two ACNs would step in and cast Physick when the tank dropped below 80%.

The truth is, healers don't need the help in dungeons most of the time. When healers need an extra hand, it's almost always because someone is not playing properly (i.e. not ducking AoEs, over-taunting all the time, etc.); but even then, often it only requires the healer to put more emphasis on healing and cut back on DPSing to fix it.

I don't see a problem with playing dungeons and Crystal Tower stuff as a class. But I do see a problem if it is "justified" with action that isn't needed.