This is because you play on Hard. It just gives hardcoded buffs to AI units, like morale. For example on Very Hard battle, AI unit will beat same player unit with 5:1 ratio.

Missile units are very strong in DeI but remember that game uses HP system so archer unit might do 50 kills but at the same time it dealt damage worth of 200 kills, making AI units much more exposed for cavalry charges and melee. Especially on rear throws, which are very strong in DeI, javelin units will decimate targets.

Now Cav is near OP in DeI but don't charge into fresh units and expected them to do great. With repeated charges, there arent really any units that can withstand best cavalry units, not counting running into pikes. Each charge does more and more damage, so first charge might only kill 20 people but 2nd charge will kill 30-40 people and so on. There is nothing stronger than Horse archer/cataphract stack in DeI. Another cool detail about TW games, cavalry is not really using charge bonus, it uses mass for the most part (sadly cant be shown in UI), while charge bonus is applied AFTER charge already stopped in case of cav.

Ideally you want to weaken enemy units with ranged units but don't overkill (as in, dont shot at enemy till it routs, even 20% of casualties on a unit might mean 40-60% of total unit HP is gone), then send in cavalry for cycle charges to finish them off.

Flanking and rear attack morale penalties are higher than in base game. Granted, flanking morale penalty is not super high because even in WH3, that penalty is often applied to frontal combat. Fun fact, vanilla game does not even have flanking morale penalty, its set to 0 there, while its -10 morale in DeI. Rear attack morale penalty is -32.

All in all, first issue is playing on hard, second is understanding game mechanics.

You can always join DeI discord to learn how to adjust your strategy to get better and get to know the game more.

He is onto something, I've testing multiple battles in towns and field where I surround the enemy and they just kill my army while surrounded . Something is going on, even when you kill the General they are still not breaking . This is new since you guys removed the Beta patch .
It could just be the horrible Camalian troops as I am using Gome atm .

Beta increased morale penalties so feedback was that at times it was now too easy to break enemy.

I believe this is due to the game engine being based off of the shogun engine which prioritizes duels, and 1 unit being surrounded by 5 will literally ignore 4 to duel 1. While so many people seem to praise Shogun 2, (despite enjoying it) I see it as the downfall of the entire TW series.

That was already added in Empire Total War.

Rome 2 was the game that added multiple attackers at the same time back, which you have in DeI too in improved form as we removed these too long sync animations that dont end up with death, so that characters are not locked in them for few seconds.