I'm such a history buff, and always have been, so Upstairs, Downstairs has been a favourite since I first saw it. The beauty of seeing something like that when you're quite young is that with every consecutive viewing, you "get it" a little more. :)
I know what you mean about the mentor/protegé dynamic. It's a favourite of mine too. Luckily, I don't pay much attention to what's considered problematic. (Or I'd have to give up on a lot of my favourite pairings. lol) I never write non-con, so things like an imbalance of power and such are something I only ever use as, well, a kink basically, never an excuse to be creepy. :)