"Flight Visibility" is not the reported metar or RVR. As defined in FAR 1.1, flight visibility is how far you can see from the cockpit of an aircraft in flight. So if you see the airport or the approach light lights three miles out, you have three miles flight visibility. At 200 feet on a three degree GS if you can just see the end of the runway you can see ~3000 feet or about half a mile. So you're good to land.