just want to throw some of my thoughts out there.
Could it be that the bees themselves are trying to overcome the varroa problem? What I mean by this is could it be that the bees swarm sometimes for the exclusive purpose of reducing mites in the hive? And if this is the case if we allow nature to take it's course in the swarm situation and not get involved (catching and re-hiving) would it or could it allow the bees to naturally "control" the mites in their own way?
Please do not crucify me...I have no science to back this....just thoughts.