Lu,
Your wrong!
All two bladers have 2/rev, all 3 bladers have 3/rev, all 4 bladers have 4/rev, etc, etc, etc. Its called N/rev.
Helicopters of all types require vibration attenuation of some sort to combat N/rev. Generally, this type of treatment equals between 1 to 2% of the aircraft's weight regardless of the number of blades to achieve an acceptable "g" level in the occupied spaces.
The Sultan