Good post, and I'd also like to join in the chorus of approval for RockyMtnSaint's post too. Both are very good points, which is why I can't completely agree with either. :D
I think Haslett was at least partially exonerated by Sullivan's inability/unwillingness to get it together in New England either. And by all accounts, for the same reasons. If Belichick & crew couldn't get Sullivan to give a damn, what chance did Haslett and Venturi have?
At the same time, your point about Richt and Seymour speaking highly of the guy, and his outstanding production at Georgia, kind of exonerates the scouting department too (which is why I can't agree with Rocky's indictment of the scouting dept.)
There just weren't any red flags beforehand, I don't think. Sullivan was going to be a first rounder regardless. I seem to remember that the reason we moved up was to get to him before Minny. Now maybe you could say Minny's front office were idiots too. But if not them, it would have been someone else.
I just don't see where picking Sullivan in particular was (overly-)"risky" any more than picking anybody is. Now trading a 1st to move up is risky, but it's risky regardless of who you pick.
So to summarize, my opinion is that it wasn't so much Haslett's fault for not getting him off his butt and away from the buffet table (because Belichick couldn't either) and it's not so much the personnel people's fault for picking Sullivan in the first place (because there really weren't any red flags that I can recall.)
It came down to the old saying: "You never know how a kid is going to respond to all that money." In other words, it was a simple case of really, REALLY bad luck. We picked Dr. Jekyll, gave him truckloads of cash, and it turned him into Mr. Hyde. Would have happened to anyone else who would have taken him, just happened to be us.