You should be able to drop onto any of the airborne platforms where the ballistas are situated: they'll stop shooting at you once you're in human form (though beware any already launched missiles as they may still hit you). That should give you enough of a chance to recuperate so that you're ready for another round. 
Edit: bah, Raze beat me to it and it seems my advice was incorrect anyway. Double bah!
Last edited by Vometia; 15/02/11 03:01 AM.
