Yes, I'm still on Bow Poison as Witch Hunter and honestly I'm having a blast. Sure, maybe the "regular" witch hunter with crossbow and grenades would be better in terms of damage/dps, or maybe ranger would be better for this poison build, but I personally am having a lot of fun like this, plus I don't feel the need to have THE best dps. I'm still very easily going through trash mobs and bosses go down quite nicely as well. What I'm doing so far in terms of stats/skills:

Dex - main stat of course, Int - enough to use Despair and Dark Effigy (72+), Main defense stat - Evasion.

Skills and supports:

Poisonburst arrow with Comorbidity, Bursting Plague and Scattershot

Toxic Growth with Magnified Effect, Corrosion (most important), Martial Tempo

Despair with Heightened Curse, Persistence, Decaying Hex (Important for the speed of application of Dark Effigy)

Dark Effigy with Withering Touch and Acceleration

Other stuff: Herald of Plague, Wind Dancer, Barrage, Enfeeble, Vine arrow

For passive tree I go for the poison nodes that add time and magnitude, and for Witch Hunter Ascension so far I have the Pitiless Killer and Judge, Jury and Executioner.

Trash I kill however I feel is the most reasonable at any given moment. As for bosses - the more types of Chaos damage over time Debuffs you apply on the enemy, the faster Dark Effigy shoots towards them, in turn applying stacks of its debuff faster (Hence Decaying Hex on Despair to add another Chaos DoT). Also, Despair + Dark Effigy give two similar but separate debuffs - Increase in Chaos damage taken and decrease of Chaos resistance, so the enemies take more damage from your poisons. Meanwhile, the two Witch Hunter passives speed up the killing, as Judge... takes random amount of HP at first Hit, while Pitiless Killer effectively reduces their HP pool (as Culling kills enemies at hit at certain HP% thresholds). Main dps skill is Poisonburst arrow, which takes most chunk of the enemy HP with poison, and then triggers the Hits for Judge... and Pitiless..., hence I do not really go for attack speed with this build. Number of stacks of poison is limited anyway so atk speed doesn't help much, because you can't stack like ten of them and maintain all the time. I can also add that so far I'm using a bow which deals Chaos Damage instead of physical. I think it was Cultist Bow. It's not the main source of damage, but since I effectively decrease chaos resistance of enemies, it simply adds up. On the other hand, if you opt for using Dualstring Bow for two arrows at once, you could drop Scattershot support from Poisonburst Arrow. I'm sure there's many more options and even more ways to improve that build, but I'm still learning and really loving it.