[1.0.0.5][Caster][v1.0](u)(vid)(g2) Acid/Poison Witch Hunter

I played in crucible couple days ago and a guy was using this build with a chaos variant (using grim fate weapon). He was litteraly one or two shotting everything even at wave 140-150 with 6th spawn in gladiator. He was also very tanky at the same time.

He told his build was legit but I really can’t understand how. Has anyone tried to use this build with chaos/poison damage and achieve such results?

which is the build chaos variant ? I can see it? thx