Well, that problem is easy to solve: currently the "j2o rank" is determined by the total number of reviews. I will talk to the responsible persons to determine it by the number of reviews with actual ratings (not including N/A reviews).
By the way, the nice member statistics page makes it very easy to find out which reviewers are good. For example (heh, i didn't say i'm a good reviewer, just as an example :-) check out my ratings.php. Esspecially the average length of the reviews can show you if someone really puts some effort into his or her reviews.