Matt, I do not necessarily disagree that GD raters leave a lot to be desired.
But that does not mean that your idea of "national" raters are going to be any better. Again, whenever you bring a group of people together, they will bring their own biases to the process. It does not matter if they are national or elite or whatever, you can't go against human nature...
...unless you specifically address those issues.
If you follow a more scientific grading process, then you would have a completely different system.
If this was a scientific grading process, you would hire a bunch of raters and train them intesively on how to judge a course. You drill them on golf course architecture and history, then you will take them out to various courses under a tutelege of a renowned expert, say TomD. Tom will tour these courses with raters and ask for their opinions and ratings and then critique them on their ratings.
After spending a great deal of time with TomD and once TomD is satisfied that they will deliver quality ratings, and only then will they be allowed to go on their own and rate various courses around the country.
If you are suggesting that we follow this type of process to create "elite" raters, then I can agree with you that GD list will improve dramatically.
However, if you are suggesting that they select "elite" raters and just let them go with not much more training than what they do now, I am highly skeptical that you will see any difference.