If you're the one being attacked from above/behind, and you lose in the rolling scissors, I'd first think about refining your technique in the scissors.
For one, I wonder if maybe you're holding a lead pursuit, when it needs to be lag. For another, I'd wonder if you're not able to seal the deal quick enough, and lose out due to that. If you get into a long, drawn out rolling scissors, the hog will probably prevail.
If you're being attacked, and your barrel roll turns into a rolling scissors, IMO you generally begin with an advantage. He's faster, and was closing on you, so it shouldn't be too difficult to force him out front (he was headed there anyway...).
In a K4, you also have the option to extend out of the scissors while you're nose down, and he's nose up. You have better acceleration, and should be able to pull away, as long as you don't dive away. Just dive enough to get initial separation, then come back up to level flight, and then begin to climb. If the hog was rolling/getting slow, there's no way he'll be able to climb with you unless you pull up too steeply and give him the option to "cut across the corner". If you dive out too far and allow the hog to dive as well (building his speed), and then make things worse by pulling up too quickly, he'll kill you though.
