Spell slinging priests go back to the Conan books, and for a more recent (if somewhat self-referential) example, the Riftwar series. The cleric class is a D&Dism based vaguely on Bishop Odo, but an easily accepted D&Dism because it slots quite easily into swords & sorcery fantasy tropes of medieval arms and armour, crusaders, priests, prayer, spirituality, healing magic, miracles and god worship.But who is to say what genre is appropriate for fantasy, and which one isn't. For example, from all the fantasy that I've read (outside D&D based novels), I've never have heard of spell slinging priests. Or at least, not in the same way as D&D. So for me I've always had trouble reconciling the cleric class my assumption of a fantasy world.
I agree that the cleric class is a gamist thing, and a "not exactly" priest, and is somewhat uncomfortable archetype, but it's definitely not out-of-genre.
Swords & sorcery fantasy defaults to an amorphous set of assumptions which are tied to pulp swords & sorcery fantasy and mythology. If the reader accepts the conceits of the genre, they can be used without explanation or challenge to suspension of disbelief (such as the concept of what a wizard is, and what he or she does, and why wizards are usually associated with medieval style settings). I think that you're painting yourself into a corner if you're trying to pretend that trains are something people associate with swords & sorcery fantasy, or that there's little concensus that they don't belong there without a explicitly defined and convincing context - which we haven't been provided with yet, but may well receive.Everyone's idea of what should constitute "fantasy" is different. Some people's idea of fantasy is based on final fantasy games, or Steven King's Dark Tower series.