Neither. I think if healer DPS was factored in the fight would be impossible, but allow me to elaborate.
At this point, I wish I never even brought it up. When I do, it opens up Pandora's Box and brings us back to a time when the healer community was divided between two factions of healers. For some reason, people either think that I am condoning what has been determined to be inferior and lazy gameplay, or I am trying to invalidate their savage clears, or something else that is taken offensively. If anyone thinks this is the case, I assure you it is not.
I attribute the majority of those age old debates to one ability: Cleric Stance. It was the only justification heals-only healers had when it came to not DPSing. It's gone now, along with any excuse they can come up to not do it, as well as the push to get healers to DPS. I suggest we leave it that.
Going back to my initial statement, I have searched high and low looking for any kind of formula posted from the devs for the raids of today and have come up with squat. I don't want parsers of the recent raid tier. I would like an official statement. I know I am not going to get it, so what I have surmised is that no one really knows how the devs factor in the DPS. For the sake of fanning the flames, I am not going to call it "healer DPS" and instead just look at the overall DPS of all eight party members.
What I know is that if I wanted to make a fight impossible to clear, then I would simply take the rDPS of all eight players playing optimally and make the requirement higher than that. That is the only way I would answer yes to the question, "Do I think the fights are made to be impossible?" This is obviously not the case and one of very few things I can conclude using deductive reasoning. The closest thing after that is that as soon as the rDPS is higher than what it required to clear it, then it becomes clearable. It doesn't matter if this factor is 100k, 10k, 1k, 100, or even 1. Obviously, the lower the number, the tighter the DPS, and the more difficult it will be for players to clear it.
Taking that into mind, I can toss all kinds of different approaches to creating the encounter requirements. I can take six players playing optimally, the average of all 8 players, seven players playing optimally and add a certain %, all eight players playing optimally and subtracting a certain %. It really doesn't matter in terms of just making it clearable. With all that said, instead of saying healer DPS isn't factored in, I will just say not all of it is. Does that sit well with you?