I'm not familiar with the Duramax, but those symptoms sound alot like when the Crankshaft Position Sensor is going out on a Ford 7.3. The 7.3 will not throw a check engine light for a faulty Crankshaft Position Sensor.
I would think if an injector is leaking fast enough to outrun the fuel pump and starve the other injectors of fuel, you should notice a significant amount of fuel in the oil.

Take your kids hunting instead of hunting your kids.

I'd rather be LOST in the woods than FOUND in the city.

Drive a hybrid, I need your gas.

Your mind is your primary weapon. Never let it get rusty.