While I'd like to be able to queue as multiple jobs, I really don't think this resolves any of the DF issues. You assume that there are plenty of DPS that have Tank classes that simply choose to queue as DPS. I would venture that there are simply too many DPS that have chosen to only level DPS classes.

What you are suggesting will mean that the people that normally Tank will see a little more variety and the people that normally only DPS will continue to only DPS. I remember in Rift I'd queue up as DPS, Healer and Tank on my Cleric and 90% of the time I'd be tanking and 10% of the time I'd be healing. I think I saw DPS pop once or twice out of hundreds of queues.