Does "Burn" inflict -45% health damage over three turns? Does it stack based on damage/duration if it triggers for two consecutive turns, or does it only extend the duration of the initial effect by one turn?
How far is the city? In terms of whether guards could see the smoke/hear the screams and arrive quickly, or could a peasant quickly escape there?
It's far. Even running, it would take infantry at least an hour or two.