My counter to snb, is if I know a pilot has it and I see that ship start pointing its nose at me, I either activate rsp or evasive and run. In the heat of battle though they sometimes get me off guard; me living usually depends on if they pumped power into aux before subnuke. If you pvp a lot in the same tier you will start to recognize players and their capabilities. Since I have subnuke too I have to be extra careful because fed sci ships will try to neurtralize me. It is a twofold battle team v team and sci v sci. If I see a sci ship re-entering the battle I have to drop my current target and immediately engage them or risk being killed.
All you can really hope to do is stay out of the their forward arc, either using evasive, tractor beams, tractor repulsors or jamming them.