From a balancing perspective, when a crossbow shot hits the head, without the “steel brow” talent, it deals 30-45 damage to health. Somehow recently I had one of my ranged with a 70 armor helmet (undamaged) get hit in the head for 57 damage, followed up by a hit to the body that killed him. From a balancing perspective, a “normal” ranged enemy, i.e. marksman or poacher, should not be able to kill ur ranged with cover in 2 shots because of RNG in a game that wants you to play it on ironman. I really do enjoy this game a lot, but playing expert ironman experiencing this just demoralizes you, especially since replacing a good ranged either takes a very long time.
HP damage taken on headshot for Heavy Crossbow is 50-70 * 1.5 (head) * 0.7 (0.5 base + 0.2 spec penetration) – 10% remaining helmet armor (after it takes damage from shot).
30-45 is closer to what you’d see in Heavy Crossbow vs top unique helmets (350+ armor) scenario.
70 armor helmet on the other hand is almost nothing against crossbow users with specialization, even with lower tier crossbows.
I consider SteelBrow (or totally ridiculous 100+ health pool) in combination with heavy armor mandatory to survive crossbows reliably.