This piece is extremely pretty. I love the details, use of lighting, and the coloring, particularly on the hair, armor, flames and wings. Still, there are a couple of distracting points. The woman's right upper arm is a little too long; her elbow would be down almost to her hipbone. Also, the Wraith (sorry, I don't know enough about D3 to know if it's a specific character ) is in a stance that looks very awkward. The hips look unnaturally jutted back, and his positioning overall comes across as very stiff and static, especially in comparison with the Sorceress, who has all kinds of wonderful fluidity to her.
Still, overall a very nice piece! And anyway, the things I've mentioned might be the "rough and incorrect parts" you were talking about in the OP.
Holy CRAP! now that is Amazing, now I'm watching this other guy who also posted a fanart for Reaper of Souls, Seeing both your art. man. I don't which is better, but both of them I know is. Mind Blowing!