Tried how it works on very hard? In couple of games I played on that setting, and when killed (shot) about 70% of them archers get so low morale that couple volleys on them make them rout.
On the other hand I liked per men system more, but personally this new one don't bother me a lot, It looks to be important in close battles, especially when both armies regroup and there isn't much foot and cav left, there less archers is an advantage since they have more ammo.
Now in normal shotwar, there's always option to get close to them and shot over archers at foot and cav behind them. I'm not shure but full archers should have an advantage over decimated. At least untill their ammo runs out, but till then you should kill enough, to force him to atack, or enough to have advantage atacking.