Path of Exile 3.0 Duelist Build Retch - SLArcher

The Retch provides 200% of your leeched life as chaos damage, which would'nt be too fancy without the Endless Hunger, because leech-effects normally would be removed at full life. - Well, with Endless Hunger it's not removed.

Finally Vessel of Vinktar provides a huge lifeleech-amount based on your lightning damage (30% base for leg. version and 20% for the new one), which is already showing the direction they build has to take: Getting as much lightning damage as possible (more later at following points).
A few sentences about slayer being played as an archer, which may be weird at the first look, but: Skilling into headsman and brutal fervour provides benefits to two-handed weapons, not two-handed-melee-weapons. 
Even though bows are being used with quivers, they are mechanically two-handed weapons, which is why they can be 6-linked as well. - So you are not going to waste any potential here.

Duelist Barrage Builds Retch - SLArcher Introduction

The skilltree is about pathing to certain keynodes such as Point Blank, Druidic Rite, Forces of Nature, Phase Acrobatics, Arcing Blows, Alchemist and Elemental Overload. The deep pathing into witch-area probably needs the most explanation. 

Alchemist grants 30% increased flask effect, which lead into 26% lightning conversion of vinktar and 39% total lightning-lifeleech. With the physical to lightning-gem (50% conversion) and a corrupted drillneck you are able to reach up to 96% lightning-conversion this way. The dps-boost is immense and totally worth the investment.

Elemental Overload on the other hand is a great addition, because Reach of the Council has only a base critical strike chance of 6% and the build isn't really made for heavy investments into critical strike multiplier on gear or tree. To maintain the buff of Elemental Overload a total critical strike chance between 10 and 20 percent is good enough, which is easily doable without heavy investments.

The other keynodes are about... 

a) defences like Phase Acrobatics, or
b) damage through elemental penetration, like Forces of Nature and Arcing Blows, or through positioning like Point Blank, 
c) utility like Druidic Rite for better gaining of flask charges and duration,
d) instant leech, because of Vaal Pact (in case you don't own a leg. Vessel of Vinktar).

On the way to those keynodes you are just taking nodes which are worth it, like most lifenode, some damage and jewel nodes. "Deal with the Bandits"-Quest should be completed with killing all for 2 additional skillpoints. 

About the ascendancy-nodes: Endless Hunger is needed for the build synergy as already being mentioned. With Bane of Legends you are getting pretty much perma-onslaught while grinding and an advanced culling strike on top of it. Headsmen gives a 20%-more-multiplier, if you have killed recently. And finally: Overwhelm is kind of a useful king of the hill-replacement: Giving some utility through crowd control.

Pantheon should be used as probably intended from GGG. Use the nodes which do help you at your current setup or tasks the most and just switch them, if you are going for something else.

Duelist Barrage Builds Retch - SLArcher Skilltree

lvl94-Skilltree, legacy Vinktar-Varation

lvl97-Skilltree, Vaal-Pact-Variation

A. 1st 6-Link

Tornado-Shot as main-attack, still one of the most powerful skills at the game. The linking provides great area-damage and still powerful single target damage, so you don't actually need a second 6-link. This setup is good enough to kill the shaper on it's own and one-shoting most bosses up to t15 without any other single-target-skill.

B. 2nd 6-Link

As said above, you don't need the 2nd-6-Link, but your single-target-damage will sky rocket with it. I am using it on my weapon-swap, as don't have a 6-link body armour. For stuff like guardians, shaper or uber-atziri/izaro i just switch my weapon.

C. 3x 4-Links

Herald of Thunder with Curse on Hit and Poacher's Mark and/or Elemental Weakness. Poacher's Mark isn't a very common curse these days, but actually like made for this build. Because you are going deep into witch-area, your dexterity won't be too huge, so your accuracy won't be as well. That's why lowering the enemies evasion is very useful. Even more useful is the 100% increased flask-gaining, because of The Retch debuff and your general dependence on flasks. On top you are getting a passive way of frenzy charge-generation. Elemental Weakness is the better choice for bosses, because Poacher's Mark doesn't do a lot here. Getting both curses needs an additional curse-mod on gear of course. Drop increased area of effect, if you got the possibility. Using Herald of Thunder with Curse on Hit and increased Area of Effect grants a very reliable source of spreading your curse and - of course - deals some more elemental damage. 

Wrath for obvious reasons, plus Blink Arrow for mobility and a Golem, because it's nice to have. Faster Attacks to buff both. Any golem works. If you are going with the Vaal Pact - tree the life-regen of the stone one won't have an effect though and you should'nt take it.

Usual cast when damage taken setup comibend with Vaal Grace (for getting increased duration linked with it). Vaal Haste instead of Grace would be ok as well, depending on what you prefer more: Speed, or defense. I prefer defense.

The shown items are just examples to show the approximate direction. 

A. HelmetHide

The most important thing about the slot is probably the enchantment. +2 projectiles to either tornado shot, or barrage is a huge boost. To choose between those is about chosing your preferences. If you are grinding bosses like shaper or uber-atziri a lot barrage will be the better choice, if it's more about general grinding then tornado shot.

For chosing the right base: Alpha's Howl provides some utility with less mana reservation and cannot be frozen. Rat's Nest isn't as great as being used at usual crit-builds, but it provides enough global critical strike chance to disregard it on any other slots.

A good rare providing resistance, life and evasion would work as well.

B. BowHide

(Legacy) Reach of the Council is probably the most powerful choice here, because you don't have to use greater multiple projectiles. High base critical strike chance isn't needed and global critical strike multiplier is useless, so i don't recommend using a rare (mirrored) bow. Of course Brood Twine & Co. do have a lot more physical damage, but the investment isn't worth it. 

If you cannot afford a legacy Reach or playing a temp league you should use GMP instead of slower projectiles and try to get any rare bow with high-phys-rolls or use Lioneye's Glare (probably drop point blank then).

C. QuiverHide

A corrupted version of Drillneck not being used a lot, which is why they are pretty cheap at the moment. For my build it's the perfect fit, because playing into the main-synergy (up to 20% lightning conversion) as well as the usual synergy with pierce.

D. AmuletHide

Weapon elemental and flat physical damage, plus life are the most important rolls here. Critical Strike chance doesn't hurt, but isn't needed. Just get some useful suffixes, like accuracy (you should get a least about 250 total from gear), resistance, needed attributs, or %-lightning-damage here.

E. Body ArmourHide

Legacy Kaom's Heart is best in slot, but if you cannot afford one, or playing a temp league a non-legacy Kaom's Heart, Belly of the Beast or good rare body armour does the job as well. If you are using a 6-link chest, you don't need a second weapon setup of course.

F. RingsHide

Once again: Weapon elemental damage, flat physical and life, plus useful suffixes. Opal and Steel being the best bases, but other useful bases are fine as well.

G. GlovesHide

I am going with gripped gloves here, because i don't like the gloves-enchantments too much. Flat physical, life and some resistance, accuracy or attack speed are great.

H. BeltHide

Must have, because the guide is more or less about The Retch and it's synergy-potentials.

I. BootsHide

Some rare boots with movement speed, life and resistance are most likely the way to go. The enchantments above, plus flat-lightning are probably the best ones. If you don't need the resistance then Atziri's Steps are definitely worth a try.