Ok I did that and it helped. She actually survived when I put my guys as close to the box as possible after the prior battle.

However I didn't. It was a 50 minute battle and I ended up getting the dragon down to about 40% health. I seriously have no idea what I can do in order to get more damage on the dragon. I'm just not hurting him enough.

I am playing on Easy already so I can't turn the difficulty down. I'm using my mage to cast summons and keep people alive. My two melee fighters are standing toe to toe with the dragon, but his breath attacks are killing them. I suppose I need to get more resistances?