This is a thread where players can post about bad unit designs they have seen the AI use and suggest how they would fix them.
When I fought against Yithril they loved to build Oppressors. They are fairly standard defenders with blunt weapons, shields, PlateProficiency, Defender, and Constitution. A lot of the time they would upgrade them to plate armor. Which makes them super tough... except they end up with 8 initiative. Not so threatening. A human player can find ways to deal with units that slow no matter how much armor they have. These units would just be a lot more dangerous if they had blades or at least switched Defender with fast. With Blades they would have twice the Initiative, and they don't need defender if they have plate.
Another unit Yithril loves to build. The problem with them is simple, they have no armor. None what so ever. This game rewards quality over quantity because army sizes are limited. There is never a good reason not to give a unit leather armor. It costs no metal and makes a big difference. Allowing this unit to upgrade to leather armor would make the swarms of them the AI builds actually useful for something. In fact you could also slap a wooden shield on them.