Between low B and high B is a huge swing in talent. I would say that B has more variability than any other group.
A+ = š½ Well they vacation out in the solar system when not driving
A = Attention seekers. Are serious hard core racers that put the practice in to maintain consistency
B = Blimey! Ranges from talented casual driver to a wannabe hard core racer whose skill is just not there yet
C = Casual folks and those beginning out..
D = Dregs

E = Exceptionally new! you never know, could be a total beginning or a A+ alien starting a new account (though they tend to rapidly progress through the ranks).
Am I wrong?
Edit: What is a good B word that describes DR B folks? Blood thirsty? Bodacious? Boisterous?