I am sure there may be other causes but both cases I have personally had with the death wabble were from worn out front rotors verified by the local mechanic that had seen it before..New rotors and it was like a new rig without the wobble..
As to diesels,I have owned just one pickup with the dreaded 6.2 and I never put a dime into it other than glow plugs and maintenance of course.Several big rigs with huge cost but huge paydays also..LOL
I am not against them but I prefer a gas engine and it's simplicity and available fuel and mechanics if necessary..