Adventurer in need is ALWAYS tank

[Driskus]

Over on Aether the queue times are all over the place. Tank isn't always instant here either. I had a 26 minute wait for Bardam's the other day as PLD. Was in the middle of the afternoon too.

[Moogly]

Try playing late at night, you'll often see healers as AIN, even sometimes DPS, and yes, it is on leveling roulette.
I also often saw DPS as AIN for alliance raid, but also saw many times healers as AIN when I checked.

For the expert/70/50-60/trials I'll admit tanks are the AIN for 99% of the time, any time of the day...