From my single player experience it feels like the losses I get come unproportionally from high-tier units. Maybe I am just unlucky with the RNG, maybe I make tactical mistakes - cannot tell. What I HAVE encountered, however, is that when using "send troops" to train tactics or because you are too injured, I often lose rare high-level troops over other more numerous and squishy types. Bad RNG luck? Like 'I have 15 Aserai Archers and 1 Battanian Fian Chamion - who gets to die at autoresolve? Right...'
I do not know whether it is bad perception or something caused by the autoresolve mechanism.
When leading the troops I had some cases of bad luck like a Brigand throwing a javelin as last-ditch effort and killing someone valuable instead of the rabble left and right to them.
There are some troops that die very often in my game: Aserai Skirmishers, Aserai Heavy Mameluke Guard and Mameluke Guards on foot.
I just do not have any proof whether is a flaw or not. I mean, if you have an elite army, you will lose elite cause you don't have other troops.
I rather concur with some point NordicWill said: medicine levels absurdly low, as does tactics and roguery. I would daresay, that medicine is the skill which is currently worst to achieve and level. This might be part of the problem.
Another thing is that changing from warband to bannerlord: I was a fan of the trainer perk and invested regularily into it. And occasionally I visited the training grounds in the world and leveled up some troops myself. I reckon, I cannot here as both I cannot start with meaningful leader skills to train troops and cannot use training grounds for the purpose of exercising with the troops.
I am also not able to improve my infrastructure - if I have a fief - to have a steady influx of recruits and the means of training them. One factor is that lords of my own faction just do a recruitment spree before suiciding their new troops on raids on villages. My villages get emptied. I would rather have a setting for my notables to send troops to the castle garrison and prevent them to sell all their men to strangers - even mercs refill their troops there.
I would like to assign a companion as trainer in a castle or assign as captain of an arms branch in my army and train the troops there.
You might buy troops from a lord's garrison, if he likes you enough and could be asked more often to train troop type X for him for bonus relationship or other rewards as well. Like higher-tier units (T2+) at castles, recruits or T0-2 at villages (yes, why not include peasants?)
Last factor, that is a bit bad in my book: The game entices us to level up stuff. Once our troops are good enough to be promoted, we WANT to do that.
It is correct, that our army needs cheap cannonfodder as well, if I want to wage huge battles if we want to play both realistically and economically. Yet, the game mechanism has a kind of reward system in store to promote troops good enough - and we do. We want it. We have grinded for it...and yet, we are punished for doing so in a certain way (that is logical nevertheless - better troops, more wage, death rate).
Just my point of view. In battle, you lose troops and you should count on that. I can understand, that a cheating AI is frustrating and at some point you are severily losing the game of attrition to the point of being unable to rebuild in time. This should be checked out, if it is a general problem. In my book, lords should start with 20 recruits - no more - and start from scratch just like us. Instead, they are magically beamed out of our prisons and respawn with a usable army core. This is not right from my point of view. This might cause too much attrition for the player to bear or enjoy the game.