If I see that the "adventurer in need" is a tank, I often switch to a tank. not because of the rewards, but because of the queue times. Unfortunately, the "Adventurer in need" is broken, since I often get faster queue times as a class that isn't what it says.

For instance. I queued up as a tank for main scenario, and it was 25 minutes in waiting on 2 healers. I switched to a healer (Adv in need still was on tank) and it popped in <4 minutes).

I thought that the duty bonus was off of who was in queue, not random number generation, (cause we all know that FFXIV's RNG is f'd up...)