You can drive the tank or the healer.
Or for that matter any DPS.

Once you have Grid/Grid Custom Layouts/Clique (or Vuhdo, or Healbot) configured... any toon can be driven and you will heal as easily as driving the Healer.

The tank is nice to drive, when you need to move the boss.
Or pick up adds.
Or change the direction the boss is facing.

Another toon is nice, when you want to get an overview or what is happening...
Rather than being in the mobs face and not seeing as much of the overall picture.





During RAF...

I would personally boost, and get a lot of teams leveled...
Rather than worry about dungeons at level...