I wouldn't say you did anything wrong. From the information you provided, I would have expected your pork to have finished in 8-10 hours. Considering your cuts were smaller than my typical cut and your temps were higher than mine, your meat should have been done sooner.
I don't know how often or how long you open your smoker. When you open it you add to the time it takes to cook because the temperatures drop and the smoker has to recover. I won't open mine more that once an hour and I make it as short as possible. Have your smoke wood, mop sauce, temperature gauge, etc... on-hand are ready when you access your smoker.
Another possibility is that your temperature gauge is incorrect or improperly placed and that you had lower temperatures than expected. The gauge should be located as close as possible to the area (level) where your food is cooking. If the gauge is located higher than your food, it will most likely record higher temps.
You could certainly use higher temperatures to cook the food faster, but I would try checking the equipment for accuracy first.