I have a few ideas on how to prevent people from using the DR shortcut. Perhaps a GM could be posted in the DR with a list of the participants, to look out for anyone trying to skip the long run. Another idea is to perhaps have some players or GMs act as referees, who would be grouped in with the teams, to watch out for anyone's HP suddenly dropping.
But I don't know if this would completely prevent someone from pretending to die on accident, such as going off a cliff, so some further punishment may be needed. I don't think it should be so extreme as to say that after a person dies they are out of the competition, because some people could accidentaly die (accidentally turning on auto-run in the BD region could be very hazerdous with all those cliffs). Perhaps a lighter penalty could be imposed, such as being frozen for ten or fifteen minutes.