That was the case with the old Things, for example an old Mercedes 250D had 75Horses and 2.5 litres displacement...
But with the high tech diesels, that's not the case anymore...
The main problems are fuel injectors, turbo charger and especally the the 'DFP'...
I can't speak for the DPF but my TDI has been problem free. No injector or Turbo problems. Though it only has 97k Miles on it right now, it isn't giving me any signs of any pending problems. Though keep in mind i do my own maintenance which includes running some fuel system cleaner through the tank every 30k or so miles so far. As with all car models, designs, and engines, there will always be manufacturing defects that cause a negative reflection in the publics eyes. The bad us usually publicized much more than any good.
As for turbo problems, with the VW TDis, most of them are related to people driving the car like it was a fragile piece of peanut brittle or something. I beat the hell out of mine. Newer VNT typer turbos require rpm and load to generate a good amount of boost now and then to keep the actuating vanes moving full sweep and freely. This problem might lessen if our diesel quality here in the US was a bit better.
Something else to keep in mind related to our diesel fuel here and from what i have read about other diesel motors from non US manufactures, is that they were designed with a c-tane rating higher than what is typically found here. Usually if you can find "Premium Diesel" you will get what it was designed for or at least much closer. If you think you shouldn't have to worry about such stuff, i would agree, but don't forget how many times gasoline has been changed and is still changing to meet emissions needs. Diesel here has been mostly for freight use here for the longest time. the new ULSD is a start to more environmentally friendly diesel fuel formulation.
For the additive for these DPFs, as noted, it can already be had cheaper from other sources, as it becomes more popular, it will likely be available from more sources and the price will probably be more competitive. Besides, that article seemed like it was pricing the stuff being bought straight from the local dealer. From a VW standpoint, and probably for all dealers, that kind of thing will differ from dealer to dealer. I know some VW dealers were killing people on the price of oil needed for the PD injectors/cam while my local dealer was competitive with on-line places. As for the charge of adding it, it should be as easy as adding washer fluid from what i have read. I have not seen one up close.
And for further reliability of modern, small diesels. there are many around with over 200k miles and many over 300k that i know about. But this doesn't included post 07 models that are required to meet the new emissions standards. Time will tell.
And a speculation about why the smaller TDIs don't need these DPFs with additive, is just that, their smaller displacement. As i followed what information was available about VW diesels for post 07 import, it was speculated that the additive would also be needed. Given some more time and research, the need for the additive may be eliminated. One can only hope.
Edit: Oh as for the DPF not doing its burn off due to short drives, i've read that before a couple years ago from a Euro VW forum. But also, short drives aren't good for any motor, especial diesel of any kind. As i've told people beforee, sometimes a gasser is best for your needs.
I've read that is one reason you don't see diesel-hybrids. Don't know how true that is; probably just more speculation.