Julian,
You have made some good points to think about. The GFR results in Europe are interesting. I had a discussion with a design judge (US based) who mentioned that in his opinion GFR were leagues ahead of any of the teams he had seen with respect to their design knowledge and presentation. This was in the 2012 season.
Your last point points out something I hadn't noticed in my initial observation. There definitely appears to be a slight bias towards the smaller engined cars, largely due to the lower mass that entails. I think the main issue is that their doesn't seem to be too much of a problem for the judges if a single cylinder car is in a range of around 20kg (say 140-160kg for a non-winged car) yet if a four is not one of the lowest mass fours it doesn't seem to get a look-in.
I am always interested to see whether how well the design judges predict the overall performance of the vehicles (over time). For example if they have a bias towards the smaller engined cars and the bigger engine cars have conisistent superior performance I would call that an unfair bias. However if the reverse is true then it highlights their accuracy.
Regardless, apart from an anomolly with the non-NA teams it looks like the design scores correlate pretty well on performance. It does highlight again that the judges are paying less attention to reliability than they used to. The top 3 design results went to teams that did not complete endurance. This is similar to recent years in the US and sends a strong message to teams that a good design event score is not contingent on being able to finish all events. Given that a good design event finish is crucial to a good event finish (unless all the top design points scorers fail to complete endurance) it indicates that teams should be less conservative and reliability focused with their designs if they are chasing a win in the US.
Kev