Can we stop talking about cheating now? it's steril and have nothing to do with OP.
I'm not agree Willie that be in a Fantasy setting mean anything can happen. Seriously, beasts raiding a city during one seasons and a well etablished city vanishing? A level 1 city, ok, but other feel weird.
Now, fantasy or not, loosing a city like that affect the balance of the game. People defending the system say, it's your fault to over expanding/ not defending, but actualy the event system can let spawn some monsters that are too strong for you. So imagine you have only 3 well etablished cities because you choosed to expand slowy and BAM the game spawn a monster you can't defeat and it destroy to ash one of your city... you lost your armies + 1 city, you just left to look the monsters/players finishing you.
In fact, I find the system encourage to create many cities, so when shit happen and loosing one isn't big deal.
Monsters raiding cities need to have an impact, but it's need to be moderated. Loosing a low level city isn't a big deal. Loosing a level 3 or more can just destroy your empire if your too small. I love to have some randomness because it's flesh out the game and give it some live, but when it put you on ground without any way to counter it, it's bad and not fun. Raided cities should be a threat that force you to act, to be creative for get over the difficulties, not an event that say!"Sorry, you loose your city and all your hard work, try again!".