You can play it either way, either Move, then Fire, or Fire, then move.
So, that being the case, the scenario you described is perfectly legal.
Hardly unfair, though, it is the strong points of the single-crewed vehicle. They are doing exactly what they were designed to do, fast attack.
The vehicle is not required to have LOS to the target during the entire movement, only at which portion of the action the vehicle intends to Fire.
A squad of AR's, or even worse, a Rocket Launcher, on Wait, will take down a moving vehicle with regularity...so it is hardly unfair. It just requires some thought, some tactics, and some strategic application of firepower...