Marksmanship

Ranged Combat Training (No Marksman skill required)

 * After some training at the shooting range you can deal more damage with bows and crossbows.
 * Effects: Bow and crossbow base damage are multiplied by a factor of 1.2. Weapon weight penalties are reduced by 50%. Ammunition grants extra Expertise. (Each ammunition type adds different amounts of Expertise, which this perk is required to benefit from.)

Ranger (15 Marksman required)

 * You improved your footwork when engaging in ranged combat with light weapons.
 * Effects: Allows full-speed running and strafing while attacking with Light bows and crossbows (not Heavy).

Eagle Eye (25 Marksman required)

 * By concentrating only on your target and holding your breath, you can now aim much more precisely.
 * Effects: Adds 5 Expertise. Grants the ability to zoom in on a target by holding the right mouse button (by the default key-bind).

Marksman's Focus (50 Marksman required)

 * When fully focusing on your target, everything around you seems to slow down remarkably.
 * Effects: Time slows down while zooming in on a target. Weapon weight penalties are reduced by 25%.

Quick Shot (60 Marksman required)

 * You have learned to draw and fire in one single movement, increasing your rate of fire with bows greatly.
 * Effects: Adds 10 Expertise. Increases draw speed with bows by 50%.

Rapid Reload (60 Marksman required)

 * You have familiarized yourself with the mechanics of your crossbow and can use this knowledge to reload it significantly faster.
 * Effects: Adds 10 Expertise. Increases reload speed with crossbows by 50%.

Power Shot (75 Marksmanship required)

 * You have discovered the art of aiming at tendons and joints. Your shots will now have a chance to stagger enemies.
 * Effects: Adds 10 Expertise. Adds a 30-40% (needs confirmation) chance to stagger most targets. (Exceptions are very large or tough enemies like giants, mammoths, Centurions, etc.)

Precise Aim (20 Marksman required)

 * Your aim is now precise enough to target weak spots in the enemy's defenses.
 * Effects: Adds 10 Expertise. Damage with bows and crossbows is again multiplied by a factor of 1.2.

Piercing Shot (45 Marksman required)

 * You've learned how to hit the weakest parts of armor, making armored foes more vulnerable to ranged weapons.
 * Effects: Adds 10 Expertise. Expertise bonus from ammunition increases by 50%.

Penetrating Shot (80 Marksman required)

 * You've mastered the technique of hitting weak armor parts, making armored foes even more vulnerable to ranged weapons.
 * Effects: Adds 15 Expertise. Expertise bonus from ammunition increases by a further 50%.

Stunning Precision (100 Marksman required)

 * Any successful staggering shot will almost always stun the target momentarily.
 * Effects: Adds 5 Expertise. Any successful staggering hits will also stun the target. (A stunned target will be subjected to a paralysis effect for 1 second.)

Information on mechanics (Requiem 3.4.0)
Here is some information to help beginners gain a better understanding of archery in Requiem. Some parts of this article go deep into the numbers, not necessary to get the gist of it, but here if you need it.

1. Heavy bow and Light bow
Expertise coming from bow : 0

Differences: Categorization: Notes
 * Heavy does around twice the damage of Light.
 * Light draws and reloads faster than Heavy.
 * Light benefits from the Ranger perk. Ranger allows you to draw and aim without slowing down.
 * Heavy drains more stamina than Light.
 * Light: Hunting, Wooden > Ancient Nordic > Elven (Smithing 50) > Glass (Smithing 75)
 * Heavy: Long, Imperial, Iron, Steel > Dwarven (Smithing 25) > Orcish (Smithing 50) > Ebony (Smithing 75) > Dragonbone (Smithing 100) > Daedric (Smithing 100)
 * The top-tier craftable bows and crossbows are Dragonbone and Daedric, both categorized as Heavy.
 * Auriel's Bow, the best overall bow in the game, is Light, but comes after the most difficult place in Requiem: the Soul Cairn.
 * No craftable Light bow is available with Smithing 25. An Elven Bow is the lowest-tier option for a craftable, non-breakable, and tempered bow. Thus there is a small gap in the scaling when using Light bows.

2. Marksman tree
Total amount of Expertise from perks: 65

Analysis

Not much expertise comes from the perks, endgame ammunition provides far more expertise.

At the start of the game the Ranger perk will help a lot with a Light bow, and will allow for combat archery, where shooting without being hidden is more feasible. It's possible with a Heavy bow, but costs more stamina for drawing the bow, and for sprinting away.

The first breakthrough comes with Marksman's Focus (Marksman 50). Having a slow-time effect while zooming means hitting a target is easier, and it takes less time to adjust a shot, so effective damage per second (DPS) increases. Before this, the first damage perk, Piercing Shot, will be available. At that time, Dwarven or Orcish arrows are likely to be available as ammunition, giving a +20 expertise from ammunition, + 10 from the perk = +30 expertise total.

Only 10 skill points later comes the second breakthrough : Quick Shot (Marksman 60), which increases DPS significantly. The difference between a Heavy bow and Light bow decreases after taking this perk. By the time this perk is reached, improved base stats should be off-setting the increased stamina drain of drawing a Heavy bow. And increased health and improved armor should make stray hits less of a factor, since it's not possible to move at full speed with a Heavy bow.

The third and final breakthrough is combination of Power Shot and Penetrating Shot (Marksman 75 and 80, respectively). The first one is very defensive and makes Heavy bows even easier to use. With a chance for each shot to stagger an opponent, this provides more time to kill them before they close distance, and helps prevent them from using their own offensive skills. Penetrating shot will mean +35 expertise total when using Dwarven or Orcish arrows (recommended against normal, living targets like bandits, Forsworn, Civil War soldiers, etc.) and +50 expertise total if using Ebony arrows. Shit abd

The final perk, Stunning Precision (Marksman 100), takes a long time to reach. For a skill boost, training in the mountains with Angi can be very helpful, as she'll provide some Marksmanship levels for free. The paralysis effect is a large benefit against extremely tough enemies, like ebony vampires and Slighted. Even though the actual paralysis effect only lasts 1 second, it takes significantly longer than that for them to stop rag-dolling and stand up, before they're ready to move or attack again.

Conclusion

Marksmanship has a smooth progression overall, with several different breakthrough perks occurring in the mid and late game. However, the skill has a major issue of damage scaling against undead enemies, which will be discussed next.

3. Ammunition expertise
We saw that ammunition perks are the 2 last of the right branch and now as they are related to expertise coming from ammunition let's go for a comparison between the craftable arrows.

Note: 1 point of Expertise provides 0.25% Armor Penetration. Thus 100 Expertise will provide 25% Armor Penetration.

Analysis

Marksmanship has bad scaling against undead: Piercing Shot and Penetrating Shot only give a +6 Expertise bonus for Silver arrows, for a total of just +12. This may be fine for regular draugr, but it becomes a major problem against vampires (especially ebony vampires), dragon priests, etc.

Using Dragonbone arrows at Marksmanship 80 provides a bonus of +180 Expertise. So Dragonbone arrows on their own will provide 73% of total Expertise (without any gear or standing stones to provide additional Expertise), and a lot of damage too. This is why the difference between Light and Heavy bows at high level, is not as large as at low level, even if Heavy bows will benefit more from the Quick Shot perk. Ammunition is a very big component of the total damage, except against undead.

The difference between Ebony and Dragonbone arrows is also very significant. The latter has a +40 Expertise difference, equivalent to a Potion of Fortify Marksman 40. They also provide better base damage, and higher elemental damage when made into elemental arrows, making a noticeable difference in overall performance. This makes Smithing 100 valuable to an archer, both for the improved bow, and improved arrows.

Conclusion

Ammunition choice is as important as the bow. Thus, Smithing (or using Honed Metal) is crucial for an archer to succeed as the game becomes more difficult. The only exception is against undead. They need silver arrows to do any significant damage, but the armor penetration from these is very poor. Using high-tier arrows like Ebony or Dragonbone, with elemental fire damage, may be a better option against enemies like ebony vampires..

4. Bow base damage
Conclusion

The base damage difference between Daedric and the final Light bow is admittedly very large. Especially given that the gap in the rate of shooting between the two bow types diminishes, once the Quick shot perk is acquired. However, knowing that top tier ammunition will contribute a lot more to damage than the bow itself, the difference is not as significant as it may appear at a glance. Still, against undead, a Heavy bow works better most of the time.

5. Derived attributes and other stuff
Increasing base stamina will also increase bow damage. Buff, bonus, Fortify Stamina effects, etc. don't count for this, however. For example, Imperials receive an inherent +50 bonus to stamina, but this does not affect their bow damage.

This can be seen in the Mod Configuration Menu (MCM) under Requiem - Skills Menu. 80% of this bonus comes from increasing base stamina and 20% comes from base health. The bonus will stay at 0% until base stamina reaches 150, after which it will increase with every increase in base stamina.

Example - Level 41 : Bosmer archer with magic support.
 * 265 base stamina, 100-110 base health, and 150 base magicka (Magicka does not affect bow damage at all.)

Stamina will help you to move faster... I really thing it's overrated for an archer. You can even be in HA (with minimun 85% movement speed I would say). It's enough for start game. And for end game.... you don't really care that much, yes you don't want to be a snail, but you don't need the edge on speed for entering the control zone of your opponent, hit him and get out. You just need to outrun undead.... well... you will do it I promise.
 * This provides a +36% bonus to bow damage.
 * This is a significant boost, the equivalent of switching from an Imperial bow to an Orcish bow.

Conclusion

Finding an optimal spread for base stats is complex, and depends on the build. A pure archer in Light Armor or clothes, with Smithing and Alchemy (most common build) can put almost everything into stamina. However, it's prudent to ensure at least 100-110 base health along with this, to maximize on the bow-damage bonus. Magicka can also be invested in a bit without any major issues. 155 base magicka, provides 2% Magic Resistance, which is just over the required threshold before Unrelenting Force shouts and similar spells won't knock a character over.

Other notes

 * If the player or an enemy is hit with a melee weapon while having a low quality bow or crossbow in hand, that weapon will break. An Elven or Dwarven bow, at minimum, is required to endure melee hits.
 * Attacks with spells can also break low-tier bows.
 * Arrows have their weight displayed as of Requiem 3.3.0. The Quiver in the player's inventory can be looked at, for a measure of the total weight of all ammunition currently being carried.