I've kept an eye on that and haven't seen any solder wick into vias. It's just sparse enough that sometimes it's hard to tell looking through the vias if there is adequate solder there. I've had the assembly vendor do inspections and they always say they are soldered, and they haven't complained about the via size.
I would expect bad noise as well as thermal problems if the pad was not soldered, but boards with the noise problems have turned out to have fairly good soldering on the pads so that is probably not it.
The fan grounds are tied into the ground plane about an inch from the regulator. The same grounding exists for all the fans so it doesn't seem like there would be fan ground connection problems with the ones that had noise problems. We don't have enough samples with the problem to isolate it further right now.