The mechanics of Martial Prowess and Martial Masterys have been a big impact on HE balancing and I feel like the mechanic is more problematic in its current state. So this is a short lookover.
In the tabletop Martial Prowess was a rule that allowed the HE units to fight and fire with an extra rank. Normally a unit with spears could attack from both the first and the second rank with the High Elves this extended to the third rank. Meaning they had a far greater offensive punch then you would expect from just their stats alone.
CA implemented Martial Prowess by tying it to a unit health pool to represent its loos once sufficient damage was taken. However the nature of the buff is focused on Melee Defense counter to the tabletop implementation. They also added it to lords and heroes making them benefit from a mechanic that they rely had no connection too. Unsurprisingly this meant that healing Lords and Heroes is more impactful.
Note these changes will have to come with some base stat changes to all HE units that are effected by it.
1. Removing Martial Prowess and Mastery from Lords, Heroes and Chariots
2. Tying it to the actual model count of the unit and not its raw health.
3. Make it primarily a Melee Atttack and a Reload Speed Buff making it more useful on Ranged units and allowing for them to be better costed.