The combine tells you nothing that the interview won't tell you. If you do the combine, you still have to do the interview. There just aren't enough points for both. I'd rather do the group workout, and after that, get as many interviews in as possible.
Here is my own personal system that I developed if you are spending $40K per week:-do the scouting combine and group demonstration-ignore all 19 year olds, focus on the 18 year olds-interview all 18 year olds with 4 and 5 ball skills-then start at the top of your list, scout each player starting with the 5 balls and going down (remember, only 18 year olds)-if you hit a guy with 4 or 5 balls in skill, interview him