All gears equipped must be Ancient as this is a legacy of nightmare build.
LoN Barber plays like an upgraded version of the Jade harvester set, much like the LoN Bombardier is to the Invoker set. The caster WD suffers from survival issues mostly due to random single monsters coming to you or stray arrows hitting you from range. Often these situations prove fatal and can happen at any time while you are doing your spell rotations.
1) Henri's perquisition is the single best survival item to prevent most of these deaths, buying enough time to react to unexpected arrows/stranglers and re-position your character.
2) Spirit Barrage : Phantasm rune (Gazing Demise) being casted 3 times acts as 3 freezing fields with 50% chance per hit to freeze anyone caught inside. The freeze will help boost toughness through the bracers.
3) When in trouble, either spirit walk away or cast Horrify > drop 1 spirit barrage on monsters hitting you. The single spirit barrage acts as a freezing field. Don't use horrify just for the armor buff without crowd controlling anything.
Most of your damage comes from Spirit Barrage. For average trash mobs, cast 3 spirit barrages on them after grouping up and watch them pop. For stronger trash mobs or elites, you'll want to cast haunt + locust on them specifically to enable the 300% boosted damage from your cubed Ring of Emptiness.
Spirit barrage works like corpse explosion. The accumulated spirit barrage damage explodes after a few seconds or when the mob dies. The explosion due to the barber hits a 15 yards radius, hence 10 mobs grouped up leads to 10 explosions. Similar to the monk's exploding palm, mobs dying can lead to a chain explosion. Being able to locust+haunt the elite prior to chain exploding the grouped mobs is great but not at the cost of your life. It will take time to learn how to do it safely.
Play style : Group up mobs, drop crowd controls, 3 x spirit barrage on pack and watch them pop. Locust + Haunt stronger targets that can live through 3 Spirit barrages. This build involves no manual buffing which all witch doctor builds are familiar with. You do not need lots of fetishes up to have toughness or Soul harvest stacks up for toughness or Giant toad up for toughness. You will work with your innate (52% from LoN 13 ancient, 50% Aquila of Cuirass), in combat locust swarm 25% damage debuff and random freezes from mobs for toughness. If you are hit, you will have 3 seconds to re-position to avoid being hit by the same mistake through your cat offhand. You will also not need to stare at Convention of Elements buff icon for permission to cast spells. How much success and fun you have in this build depends on how well you manage your crowd controls and position in fights.
Pros of this build :
Explosion, Strong Aoe, no buffs management, lots of crowd controlling options, no buffs to cast, no convention of elements buff to observe, everything is on the battle field. Lots of fun.
Cons of the build :
Not a boss killer. Like the Jade Harvester, much more difficult than most other builds.