He is PERFECT, DVS! Fabius is my favorite Chaos character, and I think you captured his personality perfectly. The sneer, the arrogant eyes... you nailed it. You can tell by looking at his face that he will always be staring at a point a couple of inches above your head, and if he deigns to notice you at all it will be on the same level as you noticing an ant.
My buddy is a World Eaters player, and has a huge thing for Kharn. I'm going to copy an email below that I sent to him explaining why Fabius is just a badass. This is also why I'm excited to see this. Can't wait to see it painted.
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Say what you will about Abaddon and Kharn; yeah they're scary, and Lucius is good old fashioned nightmare fuel, but I think the downright freakiest person in the Chaos book is Fabius Bile. This is a guy who has turned whole worlds into shambling horrors, created the Noise Marines (who are pretty awesome) and does enough medical experimentation to make Ork Mad Doks go "dat just ain't right." Not only that, but he now has pure warp energy pumping through his veins instead of blood. And he wears a lab coat made of human skin.
Plus, he decided to stop worshipping the Chaos Gods because "they have no more to offer him."
THAT is someone to be afraid of.