What is your reference point, in terms of what you are accustomed to for reliability? The Mk4 in your sig?
Touareg TDI is a highly complex luxury vehicle. Totally different kind of machine versus a far simpler Mk4, and the Mk4 came from a different era of emission controls as well, which creates an additional huge difference in complexity.
Generally whenever you increase complexity you increase the number of potential failure points and the perception of reliability deteriorates as a result. No exception here. They are very rewarding to drive but you pay the price when they break.... And as they age, they won't be as easy or cheap to keep on the road as the older cars were. (Granted those early gen TDI cars more or less set the standard for long term viability so that may be an unfair comparison...)
I got to drive and get up close with a few of the V10 trucks when they were new and we saw them come through the shop a few times (fortunately not often since they were mostly still under warranty back during the years when I was turning wrenches full time). Amazing machines, but I didn't have to spend more than a few seconds looking under the hood to know I would never want to own one myself.
