There's a mod that raises default base HP to either 125, 150, 175 or 200. Combined with collision fix mods, this made battles less chaotic, more organized and actually last for an amount of time that my brain could register. (I played with 150 and 125).
My problem was that completely unarmoured peasants were no longer getting one-shotted by cavalry with lance on horseback, unless the lance was couched. Or by an optimal two-handed weapon hit to their heads. The damage just doesn't go up to 125 or 150.
I really think changes that needs to be made is primarily to armour effectiveness and collision physics. Once this is done, heavily armoured units will be much more durable, barely armoured units will remain fragile, and with collision physics improvements/fixes will ensure that everything doesn't turn into a gigantic moshpit.