AI poor town defense!

[IHV]

I started my new Rohan campaign and played it differently this time on many aspects one of them beeing my Lord Theoden whom i sent straight away to the eastern border of Gondor lands to help keep Mordor at bay.
All the campaigns so far Gondor has been overrun by Mordor and then they started attacking me, so it seemed like a wise choice to prevent that from the start.

Now i placed my army next to E.Osgiliath to help defend the town, my first surprise was that my army is considered under siege so i cant withdraw even tho im not inside town itself.
Second surprise was when i saw how Gondor (AI) placed his troops to defend the town.

Spoiler Alert, click show to read: 

Look at the minimap, no wonder Gondor cant hold against Mordor if he defends like that. Altho battles without me are autosolved and arnt a failures like this. Mordor was inside before i got to the battle, but luckily my charges in the rear saved the day and people of Osgiliath can sleep safe one more night.

Spoiler Alert, click show to read: 

Was that a one time bug or is it going to be like that every time i reinforce them during siege, in last case i might aswell keep my army further away, since it was quite a ride to get to the battle and my men were tired once they entered and at times i thought its going to be impossible due to the fact Mordor kept unit of spearmen at the gates

[Neige]

I think that is because Mordor had a spy in Osgiliath. When you have an enemy spy in your town, your army will be scattered at the start of the battle. At least as far as I remember, it was so in vanilla.

[IHV]

Also whats up with these situations:

Spoiler Alert, click show to read: 

I get called to the battle but no battle takes place for me nor do i lose any men, but my army still moves to the battle location.

[Muffer Nl]

Did the Gondor army fight? Maybe Mordor retreated because the Gondorian army was much more powerfull.

[IHV]

Did the Gondor army fight? Maybe Mordor retreated because the Gondorian army was much more powerfull.

First time they retreated (Mordor) but Gondor attacked again and i was called again into battle and as far as i know you cant retreat twice so there was a battle but not for me included.

Same situation happend to me 2 times while playing as SIlvan Elves and Dale asked help.

Also for the first post, a little bug, when i sounded horn as reinforcing army there was no sound what so ever during the whole battle. Its nothign really just to let you know of a bug.

Atleast Sally forth worked like it should.
I wonder why i havent done it like this before, ride between Cair Andros and E.Osgiliath with my Theoden riders and murder orcs and aid Gondor, Cair Andros was sieged by 1 mordor army and second bigger one stood next to it, i utterly destoryed the bigger army and on Gondors turn i assisted him during sally forth.

Spoiler Alert, click show to read: 

Damn fun and good game just cant get enough of this

"...And Rohan shall answer..."

[Muffer Nl]

Oh and BTW about the problems with the AI ->
I´ts the ing AI man! It IS stupid!
Whenever the AI does something your response will always be: this

[Ivan Bajlo]

Look at the minimap, no wonder Gondor cant hold against Mordor if he defends like that. Altho battles without me are autosolved and arnt a failures like this. Mordor was inside before i got to the battle, but luckily my charges in the rear saved the day and people of Osgiliath can sleep safe one more night.

IIRC walls in both Osgiliath are badly damaged and AI never repairs them (costs is around 1000+ so he could be out of money, I know AI starts building like crazy if I give him 10-20000), this makes AI always place extra troops around damaged section of the wall (which seems to have chance of moving around each time you start new battle), no idea if this is from vanilla hard-coded or some new AI script designed to prevent human player exploit but it creates another huge exploit and screws up AI defense since it doesn't redeploys troops until after town center has fallen.