"theoretical damage limit of a inarius poison scythe aoe necro is extremely high, especially if your group has a mob pull ability that stacks mobs on a same pixel (inarius poison scythe could potentially do this with briggs + tragouls scythe by itself, but there are supports that could focus on this) to actually get its area damage making it even more. calcs suggest that starting at 5 mobs hit inarius beats firebats WD and only gets much better than WD from there."
The theoretical damage bonus limit of Inarius Poison Scythe (Leger´s Disdain) is at 27 Mob "density". The Essence Pool of a Necromancer is a maximum 330 with Overwhelming Essence and both main and offhand with 20 essence as secondary rolls.
With good and experienced group, one swing with the scythe hitting 27 mobs is regularly achievable and restores 324 Essence that you have to dump with preferably the Singularity rune of Skeletal Mages.
And this is where the practical limitations come in with the Inarius Poison Scythe or Generator Necromancer. If you have to use Skeletal mage in-between every scythe hit, it might cripple the huge potential of the build.