When you say ringers I assume you mean cars that dominate at the top? I think that's unavoidable whatever you do, these cars are always going to exist, that's why I think it's very important the leaderboards are easily filtered. So
But yes, I think one leaderboard for each car on each track is unrealistic. They need to generate classes (They already use them in seasonals, really) and use those for leaderboards. 350PP, 400PP, 500PP, 550PP, 600PP, 650PP, 700PP etc, then as I say you could filter them so if you only wanted to see how you compare to other 500PP Honda NSX '92 you can.
I think that would be better than nothing, personally.