Unfortunately, although I know that I've come across this kind of relationship more than once in forty years of reading fantasy novels, I can't think of an example at the moment. Your assessment of the L/A dynamic sounds like exactly the sort of thing that was going through my mind, though. Actually--it reminds me a bit of the relationship between Ben Hur and Messala in the movie (and working on Stephen Boyd's assumption that the two had been lovers as boys), where there's the power relationship of conqueror and conquered that can never truly be overcome, and had the two charcters gone back to being lovers as adults this is pretty much what would have happened to them as well.

I've never seen a truly sympathetic Arthur, and I can't stand Clive Owen. I don't understand why Lancelot and Guinevere continue to be the focus of the various movies when the more Celtic and pagan Arthur/Merlin thing is much more interesting. The exception would be that tv mini-series with Sam Neill.