The heat issue on my wife's Passat was a clogged heater core. Apparently rather common. The good news is you can replace the core without removing the dash. The bad news is there are a few over complicated German car features that make it still take all day.
I have a 2012 Jetta TDI. It has lower miles than most owners but it's mostly because I have two vehicles and split my miles between the two as I'm the only driver of both.
The car has not had the Diesel Gate "Fix". Instead I hae the ECU re-flashed, did a DPF and EGR delete, a new down pipe, all installed by myself.
The car gets 40+ in local driving and 49-53 mpg on the highway.
In the rain I have to be easy on the throttle as the tires will break traction even with traction control there's so much torque available.
VW offered much cash to owners to bring their cars in for the "fix" but since I had already done the mods I elected to pass up the cash and enjoy the performance and fuel economy it
provided. I don't regret it!