This build is aimed at very fast farming on high torments or low GRs (2-4min runs) and rivals the efficiency of the evergreen Multishot build. The reworked Holy Point Shot (Impale now throws two additional knives) makes this build good in patch 2.5.0. Since you deal so much damage per hit with Impales, you can jump into high torments or higher tiers much more easily than most other builds even with bad gear / paragons.
Full Shadow's set, Karlei's Point, Holy Point are required, after that you have a lot of freedom to try out different item and skill combinations. For most dps, you should go with Focus + Restraint, but for torments going with Stone of Jordan + Avarice Band + Ring of Royal Grandeur is really good as well once you have enough damage to oneshot stuff without the damage buff. With Gogok up you will need CDR on one item (preferably shoulders), else on three items. Supplement that with attack speed on gloves and perhaps rings, stack elemental damage + chc + chd where possible. Try to get Impale damage on boots, helm and quiver. Good cube options are Goldwrap, Wraps of Clarity, Visage of Gunes, Warzechian Armguards, Krelm's Buff Belt, Gloves of Worship, Harrington Waistguard, Leoric's Crown.
The playstyle is fairly simple, just prioritize difficulties where you can oneshot most trash mobs with a crit and kill elites in no more than 5 seconds. Move through the rift aggressively, throw Impales at high progression targets as you move, and try to find elites while you do that. It plays a little like In-Geom builds without relying on In-Geom in case you get unlucky with elite spawns, so you can still operate at maximum efficiency at all times. Try to not waste too much time on single trash monsters hiding somewhere in the corner.
There's a lot of different options to play around with, for both speed GRs and torments. You can try dropping defensive for more offense (e.g. replace Awareness with a dps passive, replace Smoke Screen with wolf), you can go for full immortality with Goldwrap in torments, you can even play with Obsidian Ring and drop Dawn, for example to go with Karlei's Point + Envious Blade. A lot of stuff works!
Feel free to watch the video for more in-depth explanations and the reasoning behind some of the item / skill choices etc.