The Essenes seem to have had at least two messiahs, and the priestly one actually addresses his army with reference to Michael in the Qumran scrolls. At least 3 of the supposed archangels are referenced as being part of the whole shebang but they then still need God to come and help too. They're all kind of distinct figures from my reading of what's been translated and made available from Qumran. I'm kind of wary of Mark Amaru Pinkham's interpretation there.
Jude referencing Enoch really strongly hints towards Michael not being the same as Jesus, at least in the view of whoever wrote Jude. Michael's fifth of the seven in Enoch 20, so you're struggling to see how he's any more special than any other of the named super-angels within those writings - Tobit even has one of the others doing the 'I'm going to pretend to be a man' thing. Jude's only short but it still manages to throw in a Michael reference without linking it to Jesus, and so one is almost forced to assume a reading similar to that found in Enoch of what/who Michael is. There's an interesting theory that angels (especially Michael) became the replacement other deities for many Jews in the second temple period, perhaps Catholic saints is a parallel there, though others will no doubt have their own opinions on that.
But really, it seems to me the whole 'Michael is Jesus' thing is kind of the JWs trying to find a way to keep Jesus distinct from God. Doesn't really make sense to me, but then I don't do the believer thing and Revelation has always struck me as having to be seen with all the other apocalyptic stuff coming out of early Christianity and also pre-70 CE Judaism. It's all very Gnostic in some ways, so I guess they're right with following the early Christian church there - they're just following the bunch who got excommunicated ;)