First : this isn't a request for you to change your mod (it's fine for most people as it is), but rather some personal observations and asking for modding guidance so I can adjust some things.

The problem : I've been playing a Dacian campaign with VBM over the last week, and I've
noticed after a while that my main tactic was "engage the enemy from the front, shoot them from behind", mainly because horse archers (and other missile troops) seem to be very effective when used like this.

I've run some clean testing [1 vs 1, no mods except VBM] and after a few dozen runs my impression is that missile vs. armour is a little wrong. The test were run by shooting 1 unit of regular bow horsemen (60) vs. picked hoplites (120) from all angles and counting casualties.

When shooting from the shielded side (front-left) the horsemen made around 40 kills before they ran out of ammo, which was a bit higher than expected, but still adequate.
When shot from back/right, however, it is a slaughter : they completely destroyed the hoplites (rout at ~100 dead) with 25% arrows left.

Only standard shot (not the heavy AP type) was used in tests.

I understand that shields / angle of shooting has to make a difference, but I didn't expected it to be so big. Basically, the game treats picked hoplites as if they're butt-naked behind the hoplon, when computing arrow damage, which doesn't ring true since their armour is 60 base + 45 shield.

This problem isn't noticeable in vanilla, since the battles are over so quickly the archers rarely have the time to make a major impact, but with the slow melee kill rates of VBM, "missiles from behind" can and will dominate tactic choices, especially if one has access to cheap horse bowmen which can get easily in a position to do this.

It also means "heavy shot" is totally useless, since the reduction in range for extra damage isn't worth it when you can destroy the heaviest armoured dudes in the game with just normal arrows.

I've attempted fixing this myself by trying to increase the protection granted by base armour versus missiles. Adjusting missile related parameters in _kv_rules ("projectile_damage_armour_divisor", "missile_armour_piercing_coefficient") with various values from 0.01 to 100, had no effect in gameplay, which leads me to believe those
parameters aren't actually used in combat calculations and maybe leftovers from older Warscape titles.

Or I'm just doing something wrong ?

Adjusting projectile damage/AP for arrows did reduce the right-back slaughter, but it also decreases the kill rates from the shielded side, which isn't what I intended. If you have any opinions/ suggestions (and time to write them) I'd be happy to hear from you.

Thanks again for creating this mod.

PS: I posted this as "discussion" because it seemed too long for a regular post