I can tell you as an Ole Miss fan and watching Dart the last three years, I wouldn't think about him til at least the 3rd Round. Yes, he can run, yes he is tough as nails, but he also has a verrry bad habit of trying to hit deep shots on what seems like every pass play. He locks in on his first receiver and if he isn't open it's time to take off and run. He's got a decent arm but not a cannon.
I've read on the OM message boards (so take this as you will) that that is pretty much all LK asked him to do, make 1 read. It's said by the guys that cover OM for 247Sports and on3.com that the film room will be where his draft position is decided. Can he explain to NFL coaches the progression of NFL pass plays from option 1 through the progression to the checkdown to the RB?
Which brings me to another thing. It drove us OM fans crazy that he would throw into double and triple coverage on a 30+ yard pass instead of hitting his TE (who on numerous occasions would be wide open by up to 5 yds) 6-8 yds downfield or checking down to his RB for a 2-5 yard gain. It's like a checkdown was his kryptonite.
Now, can these problems be coached out of him? Possibly. But Kiffin couldn't get him out of these bad habits (assuming he would want to) so I don't know if another coach can.
So 3rd round or later? Probably. Anything earlier than that would be a mistake, IMHO.