Right off the top of my head, I'd say you might want to check out BSG, actually. There isn't a huge amount of actual D/s, but power dynamics in subtler ways are explored all the time in the femslash. Plus the source canon is fantastic. *g*

Also I see you're in HP, and I actually feel like there's a lot of that in hp_girlslash, although I don't read much of it as I'm getting out of the fandom.

I may have to have a think about this, but if I come up with other ideas or other thoughts I'll let you know. Thanks for your input!