Gnosis is holy insofar as it refers to an experiential encounter with Divine Grace; it becomes heretical when it functions as a wedge that separates the “haves” from the “have nots,” thereby creating a spiritual elite, marked by a strong dualism (rejection of the body = rejection of matter = rejection of the ‘unsaved’).
Put another way, profane gnosis deals in certainties and absolutes, while holy gnosis deals in relationship and experience.
I've seen enough Quakers who have palpably lived in the life and in the Spirit go through periods of spiritual drought--and enough charismatic and vibrant Pagan priests and priestesses whose lives are a wreckage of petty conflicts and broken promises, that I know the truth of this. Hearing the voice of a god does not make you into a spiritual "have"...and not hearing one does not make you into a spiritual "have not."
Gnosis and the direct encounter with Spirit is incredibly precious. But it's a gift, and it isn't always given as a reflection of how deserving we are. Maybe the measure is how needy we are, or how effective we will be, or some other thing I can't begin to imagine. But I know that, much as I treasure the moments I can sense a direct communion with Spirit, I don't get to claim it as a personal merit, and as soon as I do, I'm blowing it.
Listening for the voice of Spirit is one of our jobs. But it doesn't always come in bright, flashy, neon colors that the people around us, or even we ourselves, will recognize. In the area of mystical religion, a little humility goes a long way.
If you've never stopped by McColman's blog, The Website of Unknowing, I do recommend it.