In my opinion, hybridity is a buzz word, and it is problematic because many in our field are applying it too loosely. Often I think that it is being used to try to dress up our field and discussions so that it appears that we are saying something new. There is a tendency in many fields to use arcane insider language instead of transparent. This has always been a gripe of mine about the field of philosophy, and I resist bringing over this language into my own writings UNLESS it is going to help us.
The usage of hybridity is confusing in our field when it moves out of the arena of imperialism and post-colonial analysis where it can be argued to make some sense (but, even the scholars who study post-colonialism cannot agree if it is a best term to use or not!).
To apply it as a descriptor of the tradition of early Judaism-Christianity (pre-Nicaea) - to call this a hybrid - is misleading. It is a "single" tradition that develops positions internally that eventually, through normation, compete and force the consolidation of two separate and different traditions with common heritage.
Gnosticism is not a hybrid either. It does not represent the mixture of the views of a colonizer imposed on the colonized. It is the Platonic world view made biblical by people who wanted to think in these directions. It has nothing whatsoever to do with post-colonial hybridity and imperialism.
Gnostic movements did, however, make other Christians anxious, but then other forms of Christianity made certain Gnostic groups anxious as well. I don't think this had to do with hybridity producing colonial anxiety. I don't think that Irenaeus really cared whether the Gnostic groups laid claim to Christian tradition - what he cared about was the fact that some of his own church members, including one of his deacon's wives, had joined a Gnostic church down the street from his own. This led him then to begin to criticize the Gnostics for not really being Christian, but trying to trick people into thinking they were Christians by stealing Christian language and ritual.
All religions may indeed be syncretistic. But this is not a reason to discard the word or replace it with hybrid (which is a word that has too much baggage from the sciences and from philosophy, and is not being applied carefully enough in our field). To say that a religion is "syncretistic" isn't the point. The point is to describe and analyze the way in which this is true. Then a whole range of possibilities presents itself in terms of politics, normation, religious identities, and all the rest.