I think this is as good as it gets in terms of Skill Trees and Passive Trees, now for gear obviously always going to be upgrading that. You mainly need the Necrotic Damage Per Skeleton Mage Idols and % Spell Damage for each Mage etc.
YouTube Vid Guide : https://www.youtube.com/watch?v=IZrxsArk5Ow&feature=youtu.be
You mainly want intelligence on everything you can, then as much ele prots + necrotic + void as you can get on gear, try to scale armor % as its super effiecent as we get up to like 4k flat armor for free from dread shade, and with that + 100% armor is insane. Idols obviously +2 Necrotic Damage Per Idol and you want the spell damage per skeleton mage.
Another note, you might need some sort of minion health, as at 100% I was having my mages die at 200+, so maybe up to 400% increased minion health. Gotta test more!
Thanks for reading/watching, make sure if you enjoyed the build guide, just leave a like on the vid and maybe a subscribe, as it supports what I do the most. I also stream every day at twitch.tv/apprenticecorner .
A viewer made the build too and killed Emperor of Souls with it, so def easy Mono Clearable