I think the reason we don't see Burkhead on that list is no one knows if he's coming back for his Senior season or not. He's the best "unknown" running back out there IMO.
Are there really rumblings that Burkhead won't return for his senior season? Honestly, I see no reason to suggest that he wouldn't. He doesn't seem like a guy that, at this point in time, would be picked high in the draft. I also just get that vibe from him that he's a four year guy.
Heisman lists are always crappy because the Heisman itself is crappy. Great players win it, no question, but not always the best player in college football.