The AI in Total War games? 
 
Don't they have someone there that know how to make it work? Seriously. Fighting a siege is the most tedious thing to do in Rome because siege towers are mostly broken vis a vis getting people in them. In Medieval 2, some units are broken except in auto-resolved battles because their special moves are broken in the battle map. In Empire and Napoleon, ranged units are not even hit or miss, they're just miss.  
 
Please hire the fellow who programs the AI Mods for all your games. He's the only one who can save you.