Beware of raw data without the necessary caviots.
Measured S-76B data that I once published shows that the tail rotor for that aircraft consumes about 100 HP total in OGE hover, with a total aircraft power of about 1170 HP. That is 8.5% of the power that the tail rotor consumes, probably less in IGE hover, and about 25 HP in cruise.
Published papers by Sergei Mikheyev show that the drag of a coax is about 10% higher than a single rotor helo, so that the fuel burn is 10% higher. This infers a 10% shorter range (or a 10% higher fuel load) for a coax.
With the usual disk loading compromises due to smaller rotor disks on coax's (coax's need shorter blades so they don't self-midair!), there is almost no practical difference between single rotor helos and coaxes in terms of raw efficiency.
The Dave Jackson synchropter is perhaps midway between coax's and singles, with a more tightly packaged head (5% drag increase?), and no real tip clearance hazard.
IMHO the play on symmetry is nice but never has been a driver on rotor designs, especially now where electronics can smooth out responses. For training and transport missions, it is insignificant, for high bandwidth air combat weapons pointing, it might have some merit.