One of the big rules of fighting dragons is, do not let them get off a full attack. If this means you don't get to full attack, so be it. Basically, you have to be prepared to have a way to get out of the dragon's reach if you're melee, or attack from outside of it somehow. This may mean coordinating with another PC to teleport/etc you out, though thats obviously costly on actions.

The 12d10 breath isn't so bad if you know you're going to be facing a dragon and know what type, since its always some kind of energy type and you can just prepare resistances appropriately.