I suffer from chronic panic attacks and excruciating pain in my spine. Without my benzos, my opioids would trigger a panic attack (as any other substance would). They also have a synergy for the certain type of pain I have - my pain is very severe and I need both in my system to be comfortable. The muscle relaxant effects of the benzos + the pain signal blocking of the opioids works great together. They have a synergy for my chronic panic attacks too as the benzos calm me down physically and the opioids calm me down mentally, allowing me to experience an ideal state of mind. Without opioids, benzos would be a little to sedating for me, but the combination leaves me highly alert yet physically relaxed. I don't get euphoria from benzos, that is entirely dependent on the opioids.
Take away one or the other and I'm fucked. I don't use benzos to boost the opioid experience, it is more that I am highly dependent on benzos and use opioids to attain higher functionality.
Someone said if the goal is to get fucked up then the combo is valid? That is not in any way, shape, or form my goal. Maybe for you, but not for me. My goal is the exact opposite of that.