So the rat runs inspired me to get the dlc, and oh man, the chaos warriors are as insane as you'd hope! Beastman are solid too, both actually make infantry enjoyable, thanks to their demonic gift level up. +1 attack or +1 wounds on infantry is insane usually, and +1 skill/power/defense is always solid too. Really hated orcs and thought infantry sucked, but it really depends on how you upgrade them :)
Won challenge level 7 with chaos had one warrior band with 15 warriors having wounds 2 with mist banner and protection blessing. Won me the challenge. While everyone was dead due to a LOT of artillery and crossbow as my final battle was human and dwarves. They had to grind Vs 5 groups of enemies and won. Insane.
