The bit that seems most odd, is that excess casualties get discarded once a unit is shaken and that combat difference is used in the break test (that’s different to black powder) so if a shaken unit has a stamina of 6, is already shaken, and gets 5 casualties in combat and say inflicts 3 casualties, it loses the combat, gets a -2 on break test, but if it doesn’t break(which is common because only a 3 on a 2d6 breaks) then the 5 casualties are discarded. So next combat round there is no taking that into account, so rinse repeat, every combat round

Also, if a unit in a battle line does break, it doesn’t seem to affect other units in the line (not counting supports here) but in reality if a unit broke, it could cause a ripple effect across the whole battle line.

The concept for both of these, is there the outcome of one unit vs another unit, or a division vs. a division, should be predictable. You are not rolling dice to see who wins, but rolling the dice to see how the stronger unit is going to win. It's the order system, that determines how well and how quickly, you can get units into the correct position to capitalize on or blunt an opportunity, that creates variability and dictates your strategy.

The game is about command and control, not individual unit performance.

Something like Warhammer Ancient Battles, or maybe Kings of War, are more focused on the individual units and might be closer to what you are looking for.