ANY 15+ year old car is going to have some problems and with ANY 2nd hand vehicle you are taking a certain amount of risk buying it, That's why they are FAR cheaper than a new truck.
I have spent $10,000+ on my D2a V8 over the last 3-4 years on repairs and Modifications But at the end of the day it is probably just as reliable as a new 4WD.
EVERY Brand and model of car/truck has something wrong with it from day 1, often called a common fault.
You May have had a bad experience with a D2 and I feel for you But that doesn't make Every D2 a piece of crap, I am coming up to 300,000K's on mine and I am fully confident it will do another 200,000K's Because I "MAINTAIN" in "As New" condition mechanically  like I do all my other vehicles.
An Ounce of prevention can save you a Ton of repairs.
The Previous Owner of my 2004 D2a most definitely neglected to service the truck properly which was blatantly obvious when the sump and the heads 
were removed by the massive amount of Sludge present, All of which has now been removed and the engine (Despite the high mileage and neglect) now still runs like a Swiss watch. 
You can "Bag" D2's all you like But in comparison to my 2012 Navara and my 2007 79 series V8 the D2a V8 is the "Pick of the Litter" as far as I am concerned off and on road[thumbsupbig]