Really cool trick i just found out - as your shaman is inside of any vehicle (balloon or boat), she gets susceptible against firewarrior shots - 2 shots will kill her. As you see two fireballs aproaching - or one, being the second (you will die as the fireball reaches you), click on the vehicle and disembark your shaman before the fireball hits. This way, the fireball damage will be way lower. This is really hard to do, because you need fast reflexes, and the vehicle (balloon or boat) must not be moving in order to disembark.