In a weird way, the writers leaving the nature of the Maker ambiguous means he must exist. Because to maintain ambiguity, then they have to write in events in such a way, that at least some characters might be able to justify their faith. Thus, unlike reality, where you could argue between guided "miracles" or miracles "coincidence", in fiction, miracles must happen for the sake of maintaining the possibility. And if miracles are created by the writers for the sake of ambiguity, then the writers become hand of the Maker in-setting.
Not true. Things that people interpret as miracles must happen - and that does happen all the time, since the only requirement for that is that an event doesn't have an immediately apparent explanation. Even more to the point, in the real world, people believe in miracles even after they've been explained.
That said, I don't have a belief one way or the other about the Maker in-setting and prefer to be able to keep it that way. I feel like too many fantasies try to deal with their entire respective cosmologies, and things start getting kind of trite when you delve too deeply into religion, especially when religions get inevitably proven false, because, hey, shock value. Admittedly, after the precedent set by DA2 and Inquisition, I certainly want some freaking answers at this point, so they're going to have to get into some of it, but I just hope they don't dip too deeply.
As much as I'd personally like to see the Maker disproven, I don't think it's possible, nor is it required. The idea is structurally immune to falsification, similar to solipsism or the idea we're all living in a computer simulation, which means that all one can do is argue that it's implausible on lack of evidence, and people who want to believe will always be able to cling to the last miniscule fraction of uncertainty we can't remove. The same, of course, does not apply to historical events. I want to know what really happened in the Black City, and I think they should answer that at some point. Regardless of what happened, some people will always believe the hand of the Maker was in it, but the events speak for themselves and I want to know.
Edit:
While the Maker can't be disproven, it's quite possible to destroy the belief in him by other means. It all depends on how they want to deal with the "faith" theme. I think it's likely they want it to stay intact, i.e. faith remains an important theme, simply because it appears to be a human constant in the real-world and regardless of our personal opinions about faith, removing it from the world would lessen our connection to it.