I have two very well geared tanks who I would like to dps on, I have to farm heroics to get that gear quickly. Why should I not be able to roll need on dps gear when that's what I'm there for? What then? I shouldn't queue as tank? Even though I am a god damn spectacular tank? I should just queue as dps and then get people trolling me because of my low dps because I don't have gear?
If you want to roll on dps gear, queue as dps. Simple as that. That plate dps'er that you want to roll against most likely had to site though a 40 minute queue, just to encounter a dbag rolling outside his/her spec. Meanwhile you are just exploiting your quick queue times as a tank so that you can quickly get dps gear.
In ZA/ZG I've tanked, melee dps'ed, ranged dps'ed and healed. Each time I roll on the stuff I queued as. Why? Because I'm not a jerk.