I try to put liquid penetrant in all the crevices I can find, then tap the rotor until it comes loose. Not much else you can do except keep at it. It's good to hear you're protecting the rotor and bearings. I like to use a hammer with a piece of wood in between.
After it's apart clean off the corrosion and place a light coating of neversieze on the problem surfaces for an easy job next time.
95 E320 Cabriolet, 131K