Thing that would make sense to me would be SAM as a tank, RDM as a DD, and DNC as a healer. However I think this would require DNC to heal based on the damage they're doing melee, or else the job would have to change a lot if they were going to be dancing on the backline. Considering that, the easier thing that makes about the same amount of sense is SAM as a tank, DNC as a DD, and RDM as a healer.