I think the simplest solution which would definately help is


1: remove scrolls which increase loyalty to 100, grevance to 0 OR give it a 7 day down time.
2: once public grevance hits 15~ city producity drops, units stationed in that city start to die based on the level of Loyalty + Grevance

Like damdar said... Scout spamming is literally the only efficient way to kill off a city, which is in practical...

The costs of raiding compared to the amount of units you have to send is way off ratio wise. so hummff