A pistol shrimp probably will not pair with a Dragon goby. Dragon or Banded gobies tend to stay in the open and not hide. Mine will cruise around picking at algae, between him and my kole tang they keep hair algae under control. These guys have a good sized mouth as well , mine ate a neon gobie once so be warned if there are smaller fish in the tank. Mine also really liked nori or sea weed on the veggie clip as well as any kind of meaty food.
They are a great goby, but if your looking for something to pair up with a pistol shrimp, go with a shrimp goby or watchman, you will have better luck. Besides if the pistol was small enough a dragon may see one as a meal.
HTH
Brian