For some reason the electric helis do that. I've tried adding loads of expo to roll/pitch, which helps but there is still the throttle/collective crazyness. Have you tried having a look at the heli mix settings? I don't know enough about it myself, but I've been thinking there could be something wrong in there.

The glow helis do not do this however and seem to be fine as default: Voyager 50 and Bell are the best IMO. I have a blast with the Voyager 50 [8D]

Make sure you have the heli update installed.