Looking at base missile damage on ranged units in FOTE (arrows, crossbows, and javelins), it seems that there is a nice balance to the damage types. Arrows tend to go 12-22 base dmg and 1-2 ap dmg, xbow bolts go 8 base with 20 ap, and javelins with base 20-24 and 6-8 ap.
Some variation to make things interesting.

Now, some units or shot types tend to break this balance completely, or push the damage to its needed values, depending on your perspective and opinion.

Namely:
- Taifali bow cav, Iranian Horse Archers, kushan heavy spearmen, xionite spearmen got heavy shot that give +10 bonus against infantry, other cav do not.
- Burgundian skirmishers, Alemanni armed skirmishers get +15 vs infantry on their standard shot
- Allemani spear skirmishers, Frankish skirmishers, Langobardian skirmishers, Svarog's horse raiders get +30 vs infantry on their standard shot

There may be more I missed.

Additionally javelineers get a bonus vs elephants and cav that varies from +10 to +30.

I'm not going into the discussion what damage values (without the bonuses or with them) is better for game balance as that is a separate topic.

I'm simply stating that the aforementioned bonuses makes these units vastly superior than any other units in the FOTE roster. (testing in custom battle, I've had a ~triple kill count on a unit with +30 bonus against a unit that didn't have it, testing in same conditions against same enemies).

Additionally, I'm not sure the AI even uses heavy shot. I see them use formations and abilities as they're visible on info panel when selected, but not shot type. So it could be that these situations are only exploitable by player.

Therefore, I'm proposing removing such boni (at the least the vs infantry bonus) from the shot types and applying them into the base missile damage of the units, with the variations as deemed fit for different units.

EDIT: If these boni represent unit skill/training, why not tie this with the units accuracy stat. AFAIK, although all units in base Attila have 0 accuracy, it does exist as a stat and is editable.