I think maybe we hold more or less the same opinion at this point, semantics aside. I admit to not reading every one of the last 55 pages completely so I'm sorry if I've made you restate things.
I completely agree that there are instances of wall to wall pulls where DPS becomes all but impossible for everyone who isn't amazingly skilled. I also agree that this is the most (or at least should be the most) reactive time for a healer. This also depends largely on your group. I've had some tanks do the full pull between the first and second bosses of Ala Mhigo where the only DPS I could do was a Swiftcasted Holy (more for the stun than the damage) and Assize for the MP. I don't think that makes me a bad healer even though I'm sure others out there could have done better because I pushed myself as hard as I could.
The issue is on bosses and small pulls when there is so little damage out there that your choices become DPSing, massive overhealing or doing nothing. Only one of those has literally any benefit. I don't know of any normal pulls of trash and very few bosses that can kill a player in one GCD without some other serious mistakes syncing up like a tank losing threat before a tankbuster. In that situation I believe it is perfectly acceptable to DPS.
Before we get into 'not everyone knows that about every fight' that is an excuse I don't accept because we are all playing on internet enabled computers and PS4s where YouTube is easily accessible.
Personally I just can't get past the double standard that we have for healing versus tanking and DPS in this game. It's been stated over and over in this thread but we just coddle healers like they didn't just subscribe to the same game. No one in the tank or DPS forums would try to justify this kind of lax playstyle amd it boggles my mind that people in the healer one have kept this thread going for nearly 60 pages.