This is a fascinating idea! I hadn’t thought of Gnostic themes in the show, but now that you mention it, there do seem to be several parallels.
First, (and somebody please correct me if my understanding from my limited reading on these topics is flawed) the Gnostics believed that the physical world was created by an evil demiurge, and was inferior to the ideal forms created by God. Couldn’t that apply to Strorybrooke? It is a flawed place created by an evil being in which the people have lost the knowledge of their true selves which could make them happy. We could say then that Regina is the demiurge, or perhaps since Rumplestiltskin created the curse, he is the demiurge and I guess that would make Regina the archon in charge of hiding the truth from people.
Second, salvation is achieved through “gnosis” because, for most of the season, Emma can’t break the curse until she has had enough experiences to finally achieve the self-knowledge that allows her to believe. Until then, Emma is a “Doubting Thomas” which could remind one of the Gnostic Gospel of Thomas discovered in the Nag Hammadi library in the 1940s. Of course, the final experience that allows her to achieve the self-knowledge is her desperation to find an explanation for Henry’s illness in the finale. While this certainly fits in with a Gnostic theme, it could also just be an example of the old adage “There are no atheists in foxholes.”
There is one other connection. Although I hadn’t thought about the theme of Gnosticism, I did recently post an idea on my webpage http://www.onceuponatimespace.com/pilotComment.html that the writers’ choice of the name ‘Henry’ might be based upon the 15th century theologian Heinrich (Henry) Cornelius Agrippa, who wrote some famous books about magic. Although Agrippa was not a Gnostic, it seems to me that both he and the Gnostics drank deeply from the well of Neo-Platonism. In fact, to my limited understanding, a lot of the ideas in Agrippa and in Gnosticism just look like warmed-over Plato (Not to be confused with warmed-over Play-Dough, although both can be messy and easily worked into many forms, but difficult to use for building a solid structure!).