Is the issue really THIS serious? I agree on the salted tile, but usually I clean up the lairs first. If you afterwards do not protect your city...sorry!
Yes I find the issue serious, and please before say sorry to people who don't defend their cities, give us your starting factions, perks and difficulties. Because how can I defend a city when it's attacked by a monster stronger than my sov army???? When I play summoner & rush the summons, I can get a decent strong army, but what can i do if i'm attacked in 2 directions and have only 1 army that can counter them? What can i do when an event pop some monsters stronger that my armies near my cities? What can I do when the AI wake up some deadly/epic monsters that choose to wander around my cities???
At best it feel totaly random, at worse it force you to use 1-2 playstyle to progress, really not good for an empire building game. I don't want loose many turns of progess to some unfair randomness where I don't have any control. I don't want be forced to reload and pray random god. Loosing a whole city like that is too much, and should an option for people who like more hardcore difficulty.
I really prefer civ4 over civ5, but the last civ added some nice features like cities HP & siege that could be used by FH :
Each city have some HP, each time AI, Monsters & Player attack a city and win, Hp dropping depending of army strengh. At each battle Militia is at full power. That would make capturing city take more that 1 turn, and that would allow militia to win over some weaker mobs like bears or keep fighting until your army come help.
City hp come back slowy each season. Each time a city is damager, some food/buildings could be destroyed.
Any system that add an incremental damage would be more interesting than a binary Keep your city/loose it on some random events.