I have shot ballet, a few times, but what I ended up doing was determined, of course, by the lighting used. Lighting is generally on the dim side, and varies, scene to scene, moment to moment, and from one end of the stage to the other. Plus, there is often a lot of contrast between subject(s) and background. What I have had luck with, is spot metering each exposure (generally taken on the face of a dancer) at the same time as single point 3D follow focusing on the same. Aperture priority, generally wide open at f/2.8, with auto ISO set with a minimum 1/320th and a max of 6400 ISO. Most shots end up being at 3600-6400 ISO. If you have more light, lower ISO or up the shutter speed. If it is darker, well, pick your evil, blur or grain. Even at 1/320th, I end up trying to grab the moment of least movement. It is amazing how fast dancers move.