There is an advantage to multiple toons beyond DOFF missions and dilithium. When I play with my fleetmates, we can roll through missions very quickly. When we've run through 3 or 4 missions we like, we don't have to run one we don't like or wait 30 minutes before starting up again. When you have a good group together, you don't want to split the team up, so you swap to another toon and you can play the same missions again on the new toons , maybe get a full fed team to run fleet alerts or something like that.