You want a bug when seiging? Try turning on "fire at will" for a siege tower on the two largest wall sizes. Talk about a gatling ballista! I stopped using this when I saw that you could clear the wall section of any defenders on approach this way. While it's fun to see a whole unit of Urban Cohorts get blasted to nothing in the time it takes the tower to set up next to the wall, it really destroys any chance of the defenders beign able to have troops anywhere near the tower on approach.

Because I want an actual *fight* on the walls for control, I leave the tower's autofire off, even for basic stone walls.