Comping MIDI and having ALL the notes in PRV at one time, is also a big issue for me! The only way I've found to deal with it is to speed comp the lanes down to a 'comp' lane, then delete the rest of the lanes that have been muted. By doing this though, I loose the ability to go back to the and re-edit my 'comp' lane.
Just occurred to me.... perhaps instead of deleting the muted lanes, I could take all the unused lanes, move to a new track and archive. Still, an awkward workaround.
Michael