If I recall correctly (please someone set me straight if I've botched this), the clause "who is in heaven" isn't a part of John 3:13 in some of the oldest manuscripts. Isn't it absent in p66, p75?
I'm fascinated with that variant though. It can be used to support the orthodox view of Jesus' divinity, but dare I say it, even a gnostic christology. Jesus as a vessel for an emanation from the All (in the form of the heavenly Son of Man). A nexus of sorts. I'm ignorant on Philo's take on archangel though. Does it have any connotations of being a divine emanation?