The point of a single Orion defeating the Sathanas is positioning. If the Orion jumps in about 1km-2km from the rear of a Sathanas, it will win because all of the SJ's effective weaponry is located on the front-most part of the ship.
Just as the Sathanas will try to turn and face the Orion doesn't mean that the Orion will leave the Sathanas' blind zone. If the Sathanas starts to turn while at complete stop, the Orion simply has to move to stay outside the fire arc. If the Sathanas wants to jump, the Orion follows it into subspace, where the SJ is even more vunerable! If the Sathanas tries to go max speed and outflank the Orion, it takes so long that the Orion probably destroyed the SJ already!
Remember in Subspace (which

ironically called Hyperspace in fs2 missions, after looking into the files), capships can't really turn to face an opponent. The Orion will still be behind the SJ in subspace. If the SJ scrambles fighters+bombers, chances are that all wings inside the Orion will be destroyed. Still, in normal space, the Orion has

of fighter defences. In subspace, it would be easier for the Orion to destroy the SJ's fighters+bombers since those ships have such a light hull