A 3 min separation from a heavy jet is just massive overkill.
Like I said, I really don't know.... I fly Piper 28 and control traffic, have no experience in helicopters. But my understanding of the wing tip vortices is that it creates a circular motion of the air, and that circular motion can be strong enough to flip stuff... though I don't see why it shouldn't affect helicopters?
Some countries allow for the pilots to take the responsibility for wake turbulence separation, if you are able to do so, you'll get "essential traffic information" about the wake turbulence, and a take-off clearance, and off you can go.