Itchy,
Remember that a NOTAR shows its coanda slots as its anti-torque device, but that is hardly effective in most environments, so that the other two anti-torque devices are also needed, and are part of the total picture. The tip thruster is much more capable, and is the true control device in a hover. The tail cone actually sees little downwash while maneuvering in winds as low as 6 to 10 knots, for example, so that the original Notar lost control in low wind hovers until the tip thruster can was installed.
At higher speeds, the coanda is also useless, and the tip thruster is terribly inefficient, so that the rudders are used.
In reality, the Notar is a cobbled up mix of three devices, and has more parts and more complexity that any other anti-torque device. It is, however, very safe for those outside, very quiet, and kinda cool.