Do you ever summon? I find that it takes alot of heat off of me while i'm fighting. It doesnt take hardly any mana and has a quick respawn time, so you can do it over and over again.
I also watch the angles that you fight from. If you can fly so that one nest or ballista is behind another, you can limit how many things you have to dodge.
The best advice though is to move erratically like Jigoku stated. I have had no problems at all blowing out the flying fortresses.
I'm at level 34 myself [ need 40k exp to hit lev 35 ] and like you, dont know where I'm going to get it from. GOOD LUCK
