The build is not bad. But there are some big flaws.
First: almost all necro build you will need the Krysbins Sentence ring, because of the 100% or 200% damage buff.
Second: the Argila Cuirass isnt a good combo with the Ledger's Disdain, in one u need almost 100% of essence and the other almost empty essence. In the same logiq u need to cut the Devouring Aura out of the build.
Now depending on the build Nayr's is more effective that the Reilenas.
Sinces the idea of the build is to kill with the Grin Scythe with the poison rune, use skill that are the poison type and have som kind of effect. The damage of the other skill dont matter, the importante is the effect. Change the poison lendary gem for what I know they dont stack with the Nayr's buff.
When leveling I was using a similar build but with nunlock trick with Command Skeleton (cold rune) to empty the essence fast and perma freeze. Bone armor (poisen rune) to stun and buff Nayr's buff. Frailty curse (with aura rune) since the essence is empty all times its dificult to cast curses. Bone spirits (poison rune) to buff Nayr's buff and crowd control. the last one was not fixed, tried made thing, but in almost all it was some thing that used corpses.