I just see this causing a problem where one doesn't exist. The problem being that the players queuing MT will be considerably less than those queuing OT because being quite honest from my experiences in DF on things like trials or 8 player raids a very noticeable number of tanks doing it in DF are only queuing tank so they don't have to wait in DPS queue and have no actual desire to tank anything because tanks are already in high demand without trying to divide it further.