To put it simply. There are no requirements for wake turbulence to be mentioned, let alone seperation provided against a light heli. Though I have long believed that more research needs to be done to establish how rotor wash affects the air and subsequently other aircraft around it. We've all seen and read about incidents where aircraft have come a cropper, even behind a light.
I had an interesting chat with a pilot of a departin P28A which was climbing out parallel to a Jetranger using the adjacent heli circuit. Apparenly he almost lost all authority over the aircraft.