The Ring can be without doubt a dangerous place.
As others have said though
1. It is a one way road, governed by German road law
2. If you drive within your limits then you should be fine. It is generally people trying to beat their previous lap times or people getting carried away that end up in trouble. You can drive as you feel at the time - I bet you'll have a smile on your face at the end.
3. Being very observant in the car will help keep you out of trouble, especially as it is your duty to keep to the right hand side of the track if someone is trying to overtake you.
4. The majority of fatalites mentioned earlier are bikers
5. It's got nothing on the M25 !
6. Lastly - mention to them that they let coaches go around the Nordschliefe on public days, so how dangerous can it be?