If you are struggling with the amount of damage you are taking then you might want to consider lowering the "Player Received Damage" Campaign Options difficulty setting.
You need to improve armor and damage calculation to protect the AI enemy from being butchered by the player too. High tier armored units dying in 2-3 exchanges just like low tier ones feels silly.
I just want to say, I have absorbed a constant supply of questions from players about the "weakness of high tier armor, why doesn't the armor work more gooder, why doesn't x troops not die so easily, why do t2 archer murder my t6 units so easily, is armor fixed yes, what mod fixes armor" and on and on and on, over the last 2 years. Please, do not underestimate the importance of this subject to the bulk of players. It an extremely common concern shared by nearly everyone I encounter and it's very rare to meet a player who thinks the armor/damage calc is good/fair/improved and such.The people playing and enjoying the game.
But why is it appropriate for high tier units to die so easily in a long term strategy RPG where the player invests resources and time to customize thier forces? I get that it works for captain mode multiplayer matches for "fact paced action" where you get fresh troops every match, but why is this style part of the vision for long, grindy, protracted single player campaigns? Why was a much more useful and rewarding unit progression and armor power appropriate for Mount and Blade Warband but not for Bannerlord?And I get that you have your own vision of what the game should be... but so do we.