Build Version
0.8C … 1st Ver.
Video: (at level 86, 0.8C)
0:00 dummy test.
0:10 map farming
0:30 lvl 100 Rahyeh battle.
Main skill
Decoy (Crit-hit)
・10～20 k dmg / decoy in LV 100 area, non buff. (50 ～70 k / decoy, full buff)
・100k ～150 k dmg / decoy on dummy, non buff. (800 k～ 1M / decoy, full buff)
Decoy Bomber Build Guide (Beta 0.8C)
pros/cons
・pros
High Single-Damage
・cons
Slow farming speed caused by Decoy’s recharging time.
(Especially, not good at cleanse the forge in monolith.)
Glass cannon.
Other offense skills are ultra low damage.
Unique gear / Idols
1 : Gambler’s Fallacy (lvl 1)
Gambler's Fallacy - Unique Ruby Amulet - Amulet - Last Epoch Item Database
(I feel potentiality of Gambler’s fallacy, at this late hour 
)
2 : Ward Trail (lvl 60)
Ward Trail - Unique Ranger's Belt - Belt - Last Epoch Item Database
For keep full life.
3 : LI’RAKA’S craws
Li'raka's Claws - Unique Plated Gauntlets - Gloves - Last Epoch Item Database
(Option)
1 : Transient Rest
Transient Rest - Unique Brigandine Boots - Boots - Last Epoch Item Database
Idol :
Maybe, Majasan Idols have crit-multi, are best.
Synergy / Explanation
It can deal 100 % crit-hit every 4 sec, from Gambler’s fallacy.
So If using Decoy-explosion, It don’t need thinking about “increased crit-chance”.
Decoy recharging time is too long, but decoy’s high damage remedy this defect.
All most mobs can kill 1-shot without buff.
In the boss battle, it need some process for full buff for high damage.
Decoy Combo example for boss battle. (In movie, 0:00～0:07)
1 Smoke bomb with Umbral assault node (100 % shadow chance / sec)
↓
2 2x Cinder strike combo with Coated Dart and Combustible node (+ throw dmg, + pene) (1st time crit-hit)
↓
3 Decoy (consuming flow)
↓
(4 1x Cinder strike combo if having time to spare (Hard-combo)
↓
5 Acid Flask with Tempered glass and Smoulder node (4x fire res shred)
About 3 Shadows generated by Smoke also throw 3 flasks, so if you have 100 % or more armor shred in Weapon’s affix, it can shred 40 % (5x fire res shred x 4 flasks = 20 fire res shred) fire resistance of bosses.
Combining Cinder’s 30 % fire penetration, It is greater damage buff.
↓
6 Shift (combination with Agility from Rogue Passive tree. Agility can increase 1.5 % damage per 1 %your movement speed (at max level)
↓
Decoy explode
※I think that Katana (AS 1.25) and Kris (AS 1.1) are best. To aim decoy’s stable crit-hit, fast Attack speed is important.
※This Decoy combo is not 100 % success.
Unfortunately, If it occur crit-hit on step 4 or 5, decoy can not crit-hit. So, decoy’s damage is about 90 % less.
In my experiments, success rate is about 70 %.
In movie, first try (0:40) is success, 2nd try (1:20) is fail, 3rd try (1:50) is success.
Stats (at level 86)
Non Buff
Current gears
Passive tree (at Level 86)
Rogue
BladeDancer
※Maybe, before lvl 60 (can equip Ward trail), learning Apostacy node (Dodge→GB) is better.
※Maybe, 2x Kris dagger style is better than dagger and sword style before you can learn 10x Weapons of choice node (150 % crit multi)
※Asuvon’s pact and Exuberance node’s full life damage buff is powerful, so for using this advantage, Ward Trail belt and dodge style is good combination, I think.
Blessing
The Black Sun (LV68-100)
(Grand) Emptiness of Ash : Crit-multi
Grand Emptiness of Ash - Blessing - Last Epoch Item Database
or (Grand) Wrath of Rahyeh : Fire damage
Grand Wrath of Rahyeh - Blessing - Last Epoch Item Database
End of the storm (LV80 - 100)
(Grand) Light of the Moon : Mana
Grand Light of the Moon - Blessing - Last Epoch Item Database
or (Grand) Bastion of Divinity : Elemental resistance
Grand Bastion of Divinity - Blessing - Last Epoch Item Database
Reign of Dragons (LV100)
Resolve of Humanity : All resistance
Resolve of Humanity - Blessing - Last Epoch Item Database
Active skills
1 Decoy (main skill)
2 Cinder Strike (buff for bosses)
3 Acid Flask(buff for bosses)
4 Smoke bomb (buff for bosses/ defense)
5 Shift (buff for bosses / escape)
Feedback from this build
There are “Mana efficiency with decoy” affix on Helmets / body and Idols. But I wish devs to change one side to “Decoy cooldown recovery speed.”
Maybe I think decoy using as damage source is rare in other builds.
Even if there are these builds, maybe it does not use “mana efficiency with decoy” affix because the long cooldown time is the biggest problem.
So, I think mana efficiency affix is enough in only one side 
Thank you for your interest !