Thanks for the response. I agree with you generally about Irenaeus, but I think that Nicea put the finishing touches, sealed the deal. There were still debates going on before that.

I also would probably not choose 'Mithraic' as my term, although Michael does. I would normally say something like ancient Mystery traditions, which include a dying-and-resurrected saviour God. There are several of these, but Mithraism may have the closest resemblances.

I also am reluctant to dismiss Paul so readily. I think he needs exploring in greater depth.