Interesting query. Personally I think healers will be in shorter supply than tanks for this. Since I only have experience with queue times in eu-english that is what my guess is for. In my experience for pugs on /2 it's always Healer>tank>Rdps>Mdps so:
Tank: +/- 10-15 minutes
Healer: depending on if you are the first or last healer to join: instant to 7 minutes
Ranged Dps: 20-30 minutes
Melee Dps: 30-40 minutes