I'm not going to say your build is good or bad. I'll just tell you this much.
With Inarius your skills have to be close range or they don't proc the damage buff from the set. The only mage rune I found that works great with Inarius is the poison rune. Otherwise, you have to go head first into a bunch of monsters to get the damage buff applied to your mages. In other words, you can't just stand behind your mages and expect them to do any damage. It's similar to proccing Bone Armor. You have to take a risk and get close to monsters to proc Bone Armor. I can't count how many times I died because of that. Now, imagine trying to manage Bone Armor + Mages... you'll probably die twice as much.
From what I recall, the gem doesn't proc the poison buff.
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.