As much as I appreciate the sentiments of this idea, from a design standpoint is just wouldn't work. The DF is specifically for filling instances for people who need the content in order to progress with people who will play with them. The most efficient way to do this is if everyone queued solo, because combinatorics. Of course, not everyone is going to queue solo so we need to makes sure at least some of the community is or else it would destroy queue times. The way to incentive solo play is that the roulette, with its bonuses, requires solo play. Allowing people to "duo" queue into roulettes breaks this and it would really mess with queue times. Generally I think it would raise the mean and the variance of the wait time. Not good.