Hi Stephen,
My guess is that the top level sailors you list will rarely be beaten by the "favourable Mozzie rating", unless the sailors on the Mozzies are of equal standing, except in cases where there are unreliable winds and the Mozzie sailor picked the side of the course with fewer holes or the right shifts.
As Gary said, if an A-class or T sailor is being beaten to the weather mark regularly by the Mozzies he needs to look further than the ratings to find his problem.
In the right winds I have been holding up well-sailed Hobie Tigers both up and downwind, but in other conditions they certainly have the edge on the Mozzie. (I`m an average weekend sailor.)
Just to consider the ISAF rating we sail off : In a 4 day regatta Tigers started 5 min. behind Mozzies and finished just ahead of lead Mozzies (1-2minutes) over races lasting 40 minutes. That translates to a rating difference of 14-17 points on ISAF system, yet Mozzies rating is only 13 points more than Tigers, so in fact the Mozzie sailors believe the Tiger rating is generous.
After all, you`re looking at a 40 year old design boat with a low aspect ratio pin-head mainsail that never drew this much attention until we added spinnakers !!

Steve