You only hear about the bad DSG boxes.
Which means that there are quite a few about. The single evidence of your dad's car is completely anecdotal.
I know around 6 people at work with Golf 2.0TDIs and DSG (Golfs/Passat CCs/Sciroccos/A3) and none have had issues. The 7 speed dry clutch is definitely the one to be concerned with and you won't see that on a 2.0 VAG unit in TDI or TSI.
The fact you only hear about the bad ones is completely anecdotal. If 1 in 100 were to fail would you consider it an issue? The 99 wouldn't be broadcasting how trouble-free their DSGs were, but you'd hear about the 1 bad one. If you keep your Golf beyond the warranty and it hasn't played up in warranty it's quite unlikely to start playing up just out of warranty (although it is possible).
VWs aren't the most reliable cars - my 2 MK5 Golfs had plenty of warranty work lavished upon them, which is a good thing - all the niggles were picked up early. A faulty component or incorrect installation is far likely to fail earlier than later.
The 6 speed wet box has been with us a long time and is far more established than the newer 7 speed dry unit. They've had plenty of time to perfect it if it was a troublesome unit.