Very good, though two things are bugging me a little.
One, The Doom Reaver seems a bit scrawny. While he seems to be in very good physical condition for a normal human, Doom Reavers are not normal humans, and if memory serves the fell blades actually make the Doom Reavers larger and stronger. The miniatures also have immense arm and torso muscles, far beyond the human norm.
Two, the Fellblade seems a little short, It should be a about as tall as the Reaver or a little taller. Also I can't tell from this angle but the Fellblade should be chained to at least one of his wrists.
Aside from those two small points this is a wonderfull piece of art, I really like the unhealthy glow effect that the Fellblade gives off, though I think if you gave the faces in the blade a slight blurring it would help, as the faces are supposed to shift.
Everything else is perfect, you have a great attention to detail like the few chain links on the loincloth, the battle wear on all of the armor and clothing, the fact you actually put niples on him (though its not as odd as the nipples on the models) and the triumphant and simultaneously bloodthirsty pose. There is also perfect proportions of your subject. I quite like all of your Iron Kingdoms art, specifically the Khador. You sir do the Motherland proud.
I do understand the things you don't like but's that's how I see the Doom Reavers. After all they are not some kind of ubermensch but "only" brutal criminals bound to the swords as a penalty legion. That's how I remember them. And if you look at the picture he has the chain at his wrist but has broken it.
After reading what you said I decided to check out my old rule book that has gathered dust ever since Mark II Premiered in the States. In the Doom Reaver Page it does say, and I quote "Twice as strong and lashing out with berserk abandon..." I refer to the "Twice as strong" bit. Even their strength stat is unnatural. it is a seven. A normal Khadoran is a five, an iron-fang pikeman mnn who marches and sleeps in heavy plate armor has a six. Even Vladimir and Schorcha only have a six strength. The butcher wins with an eight, but he is in no way normal. so now you know why I think of Doom Reavers as "unnatural"