Hmmm, that's a fair point. The nightspinner has a range of 40 inches, which isn't half bad. Maybe a second nightspinner would be in order.
But yes, the main idea is to have the guardians take advantage of Battle Focus and move rapidly into combat range after being knocked out. But, in that situation, would I really want to take a gun platform with them? Won't that just slow the guardians down?
What's the movement on the platform? Don't have my index with me. If it has a shuriken cannon on it, it can still move and shoot reliably. The platform can also tank wounds that would otherwise kill a guardian outright
The platform has the same movement as the Guardians, so there's no speed differential to worry about.