In my experience the only time groups use the single tank or single healer is when the DPS present are lacking or the party leader is not confident in the groups ability to clear with the current DPS. I admit I have made PF parties with single tank or healer options for such reasons but I think that overall I do not believe there is a major problem for healers or tanks (at this current time), sure PF parties can be annoying in this regard or even some statics but DF benefits from healers and tanks as much now as they always have.

I am actually jealous of healer and tank queue times...so freaking fast compared to us DPS. I am glad I will be making a tank when DRK comes out so I too can bask in the glory that is instant DF queues. I look forward to it greatly.