DPSing as a healer

[Tsumes]

It's not a straw man, it's the logical conclusion of your line of argumentation, please learn the difference. If you consider "always be casting" (i.e. casting offensive abilities when there's nothing to heal) an optimization for healers (and therefore implicitly optional), and not the basis of adequate play, you must either also argue that this should be the case for all other roles (at which point most people will rightly disagree with you), or you must show how healers are such special snowflakes that they get to stand around for extended amounts of time, and you have done neither.

I'm curious. What are you trying to achieve exactly? Is your aim to ultimately force every healer start DPSing? If so, you should probably stop wasting your time. If your goal is to prove a point. It's safe to say you've done it already. Regardless, I can't see anyone changing their mind or style of play based on someone else's opinion of how it should be done. I know I certainly won't, and from the looks of it, no one else who've disagreed with you will either. If you manage to get to end game on a healer, then how you do so is irrelevant. It's not a hardcore, or competition style game, you're not gaining anything by clearing a dungeon 20 minutes faster then the last guy. If your personal goal is to get through them as fast as possible. Then obviously using a random group composed by the system is not what you should be doing. Form your own. Simple.

TL : DR - Help me understand what your goal is.