Attacks that counted as Finesses Hit will deal increased damage. This damage is decided by this attack's base damage, attack finesse value and enemy armour category.

Talents like Exquisite Huntress / Deathknell only affect the Headshot Bonus Damage part.
E.g One attack does 20 damage as bodyshot, 30 damage as headshot, then the Headshot Bonus Damage is 30 - 20 = 10. Talents like Exquisite Huntress / Deathknell only affect the 10 damage part.
The important part is, talents like Exquisite Huntress / Deathknell only give good damage boost on weapons that already have a great Headshot Bonus Damage. Low headshot damage weapons benefit little from them.

For a more detailed explanation/mechanic, J_sat has couple of Youtube videos explaining the whole Vermintide 2 damage calculation system.

In Vermintide 2, depends on which Talent/Trait/Mechanic, 'Headshot' can be triggered on different hitboxes.
Enemy Head, Neck and Stormfiend Control Panel can all be counted as 'Head' depends on the context.

Universal Talent

Career Specific Talent/Passive/Perk

Base Game Trait

Chaos Waste Boon/Trait

Damage/Stagger

Melee Attack Headshot Mechanic is fairly simple. As long as the first enemy body part that your Melee Attack Hitbox contact is the head, it is counted as Headshot.

• Horizontal Slash Attack can score Headshot by aiming at enemy head level.
  
• The closer you are to the enemy/the higher the enemy is, the higher you need to aim to score a headshot.

• Vertical Overhead Attack can score Headshot by aiming above enemy head level.
  
• The closer you are to the enemy/the higher the enemy is, the higher you need to aim to score a headshot.
  
• Jumping can help you land headshot with Vertical Overhead Attack since it allows you to start the weapon swing above the enemy head level easier. This is especially useful on high height enemies.

• Diagonal Overhead Attack can score Headshot by aiming enemy head with the center of your weapon swing arc. This is mostly useful on low and medium height enemies.
  
• Diagonal Overhead Attack can also score Headshot by tilting camera angle, aiming enemy head with the starting of your weapon swing arc, landing headshot with the vertical swing part of the attack. This is mostly useful on medium and high height enemies and extends your attack range.
  
• The closer you are to the enemy/the higher the enemy is, the higher you need to aim to score a headshot.

• Diagonal Uppercut Attack can score Headshot by aiming above enemy head level and tilt camera angle, so you can score headshot with the start of your weapon swing arc.
  
• Jumping can help you land headshot with Diagonal Uppercut Attack. And this is essential to land headshot on some high height enemies.

• Stab Attack can score Headshot by aiming enemy head with the end of your weapon pole.
  
• Stab Attack can also score Headshot by aiming above enemy head level and drag down the weapon swing. Assembling a hitbox that is close to a Vertical Overhead Attack.
  
• The closer you are to the enemy/the higher the enemy is, the higher you need to aim to score a headshot. This is especially important to Stab Attack.

• Hitscan Range Attack is fairly straightforward. The range attack will hit the enemy the moment you fire. The hit zone is wherever the Hitscan Range Attack lands.

• Projectile Range Attack hitbox is a long cylinder.
  
• The size and speed of the Projectile Range Attack are decided by the radius of the cylinder and the distance between each white ball in the cylinder.
  
  - The radius of the cylinder decides the size of the projectile. The larger the radius is, the larger the projectile is, and the easier this attack can hit the enemy.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  - The distance between each white ball is the distance the projectile travels in 1 frame. The longer the distance is, the faster the projectile is.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  - Small Fast Projectile/Medium Projectile/Large Slow Projectile Hitbox Demo
  
  
  
• When damaging the enemy, if the projectile hitbox travels through multiple hit zone in one frame, the game will prioritize use Head/Neck/Weakpoint and wherever does the highest damage as the hitzone if possible.
  
  In the video, most of the projectile hitbox hits the enemy body part, but it still counts as a headshot since a small part of the projectile hitbox hits the enemy head.
  

Due to the uniqueness of Range Projectile Attack in Vermintide 2, some fast projectile can headshot enemies from the back.
The mechanic of Range Back Headshot is that if your projectile goes through the enemy's back & Head/Neck/Weakpoint in one frame, the game will use the Head/Neck/Weakpoint as the hitzone since they are prioritized.

The Head/Neck hitzone is on the red line, the back hitzone is on the blue line. They are not between the same two balls. Did not score back headshot.






































The Head/Neck hitzone and the back hitzone are in between the same two balls. Scored back headshot.






































In the video, I used Waystalker lvl30 talent Piercing Shot, which refunds 100% cooldown if you hit enemy head OR neck, and I scored a head(neck) shot from behind.