I don't know why I have a different experience from other people, in my game I don't feel like they're OP or anything. My companions gets a kill 1~5 in each battle.
I don't know how you guy get so many kills, don't you guy have problem with Shield? My HA can't get a kill that much because infantry/Cavalry tend to have shield, You can't leave them 1vs1 with enemy archer or they will die a lot.
So I mostly use them to distracting enemy's cavalry and they do a amazing job. Then I lead my cavalry to kill their archer, then Charging my infantry. At this point everyone brawl each other and you will see HA scatter around battlefield, Some distracting enemy's Cavalry, Some shooting support for infantry. It just so beautiful. And most of the time they're the one who died first.
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[Sub-mod]PoP3.8.4Horse archer AI enhancement for every units version [From finkrer Reply#131]
https://mega.nz/#!mY80yBTA!WufZG9trEJVEVL6B_qJPyVXK5ioq140NwOvgz4cIN60
(Bugs)
Infantry, Cavalry will move to the location you tell them to 'Hold Position' then they will move back to egde of the map.
How to temporarily fix this: Tell them to 'Hold Position' far more than you want them to, then order them to 'Stand Ground' when they walking near a location where originally you want them to 'Hold Position', then use 'Move forward/backward ten paces' to control them.
Can someone please help fix this bug.
This mod is perfect if only it doesn't have this problem.