No, the Netherlands grows its marijuana domestically (and exports about half of what is grown domestically).
But to be honest, it's not a huge amount. The Netherlands grows about 270,000 kg of marijuana annually. To put that into perspective, about 17,600,000 pounds are grown each year in just five US states (Washington, California, Tennessee, Kentucky, and Hawaii).
Despite our reputation, the Netherlands are now behind when it comes to legalization of marijuana.
Wherever there is a black market there is much more crime, especially of the violent variety. Looking at crime in the Netherlands, I would venture to guess that its very much like California's market pre-legalization where most growers operated as legitimate, albeit heavily under-regulated, businesses that could still turn to local police in case of robbery, threats, etc. but still have to worry about flying under the radar (like when the DEA raided a bunch of collectives in California because they were too close to schools)