Lots of overheating this year! Check other threads ... several other folks are having same kind of issues.
My understanding is that fans are not the issue if the car is overheating during normal driving ... i.e. there is air flow over the radiator. Usually, can only be: radiator, pressure, thermostat ...
Chances of a bad radiator are limited ... and costly. Chances of a bad tstat are better and pretty easy to replace at less than $20.
You hit all the normal stuff already ... have it pressure checked, maybe (grasping at straws here)?
Broken neck on overflow tank? Too high ratio of coolant to water (although this would more likely be on the margin, I guess).
Keep this thread going, please.
Let us know what happens and how it gets fixed.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg