I did that job in July. One disc slipped off, the other was stuck. I had better luck pounding on the wheel mounting surface. And I mean pounding. I conclude that it's better to loosen whatever's keeping the disc on the hub than to try to pry the disc off the hub.
If the front wheels are blocked and the rear wheels are in the air, it should matter that car is in neutral. Again, if you pound on the wheel mounting surface, it won't matter that the car is in park.