I like the idea of a small diesel in a 1500 - something designed to get great MPG, and be up to the tasks that the vast majority of truck buyers need. NOT something that is designed/marketed to tow.
In my mind, the Titan XD is in no-man's land. The 5.0 is too big, so that it doesn't get great MPG (in fact, at 15 MPG in the test, it is similar to either a 5.7 Hemi or a 3.5 EcoBoost), while at the same time is too small to have real power - I'd be willing to bet that the top engine of any of the Big 3 (or the Tundra for that matter) will out pull it.
The Titan just missed the mark, regardless of wether this reported reliability is normal or not.