This is not shocking at all. From 2006 to 2009, I was a part of several league championship teams that advanced to Sectionals using veteran League players. During that time period, the team that beat us at Sectionals and advanced to Nationals was always stocked with 4 or more self rated studs (who, coincidently, were also the best players on those teams). Over those 4 seasons, the accummulative records of these self rated players were very similar to what you have calculated for your region.
Both I and my co-captain wrote numerous e-mails to the USTA, and talked with officials about this in person whenever we had the chance. To fix the problem, we suggested a modification that self rated players would be able to play in the local league, but would be ineligible for the playoffs in the first season. Another idea was to make it so self rated players would have to a minimum of 6 or 8 matches before being playoff eligible (making it more likely that they would strike out). Either way, we thought this might help weed out the ringers... because the cheating with the self rating system is a disgrace! However, here we are several years later, and nothing has changed.
For what it's worth, I took on 3 self rated players this year for the first time on my 4.5 team. (If you can't beat them, join them... right?) Two of them had played D1 tennis in the 80's and another was ranked #1 in our section in his age group. However, all three of my players were over the age of 42 (which is how they were able to get 4.5 ratings - we didn't cheat). They were all key contributors to our wins, and my team made the local playoffs again. Unfortunately, another local team stocked themselves with 4 self rated players, all under the age of 30, who seemed to be 5.0+. One of them was a recent graduate of a ranked D3 team, who I would have filed a grievance against if they had played him against us (he was saved for the final). In addition, they have a huge cheater on their team that self rated at 4.0 a couple seasons ago despite a couple state high school championships and a good D1 college career, and now has an untouchable computer rating. The USTA knows about that guy because a grievance was filed, but they refused to act on it because of his computer rating (although they acknowledged that he never should have been allowed to self rate at 4.0). It was bitter to lose against those guys, but I figure they will all be bumped to 5.0 next year, where my guys will still be at 4.5. Besides, since most of my team is 40+, I'm looking forward to that division next year (where hopefully there will be less self rating abuse).
On that note, I'm just curious how many of these self rated ringers you've researched are under the age of 40?
My guess is that it's close to 90% or more.