Haven – "Everything is mixed up, truth and falsehood" [Campaign 3 – Mission 2]

Hey, why are you so focused on Antonshka? Crossbowmen don't attack their own units standing on adjacent tiles. That's one thing.

And what's so great about Antonshka? +15% to ranged attack is nothing.
In this case, crossbowmen will be blocked first, and secondly, when the same cavalry units are fighting on the front lines, you might have to wait or even skip turns so as not to hit your own units.

Spending upgrade points on crossbowmen (+3% damage per shot) - the ONLY ranged unit in the entire faction - is the height of irresponsibility.

Really? With crossbowmen, you can target multiple stacks at once, dealing significant damage. If there are no defenders nearby, it's a disaster. Especially for enemy light cavalry and sisters.

In the Campaigns, upgraded cavalry and light cavalry rule, not ranged units.

But doesn't it matter that they can't be upgraded there? :)
Buggy cavalry definitely doesn't rule. Light cavalry deals good damage, yes, but they can never hold the line.

What to do if the crossbowmen are taken out?

By what? Melee units can't get close to them (if you know how to protect your ranged units), enemy ranged units will deal minimal damage considering the protection bonus from the guardians, and the sisters will heal them if necessary. But! As for the AI, it only starts worrying about crossbowmen after taking out the sisters and griffons. By that time, 3% will add up to 21%-24% in the worst case.

Passive perks for defense and retaliation, and warcries.

Passive perks for defense, retaliation... Are you even listening to what I'm saying? When using a tactic that involves protecting ranged units, the features you mentioned should be there, plus morale for the guardian angel (although the AI still cheats, even with 10 it rolls more often than my 30)