This guy's work is impressive. A bit simplistic, obviously, but still quite well thought out. It would not take a lot of extra work to make the electric power source for the main and tail rotors fully redundant. Going to an even number of tail rotor motors makes this trivial, just split them half and half. For the main rotor motor slightly less trivial as actual power electronics would be involved but nothing that hasn't been done before in many other applications. One might even consider two motors but that starts to generate the usual diminishing returns in terms of cost/complexity/size/weight.
Even the 27 minute endurance is impressive given the limitations of today's battery technology. It is, unsurprisingly, very commensurate with drones of all sizes. Stating the obvious, until someone comes up with electrical power storage systems with approx. 10 times the power density currently achievable, prime power will continue to derive from piston and turbine sources, even if some of that power is converted to electrical energy for an electric anti-torque system. And that also does not address the problem of charging time.
For me the real take-away is that, looking at this effort, and Bell's work also, electric anti-torque systems using a multiplicity of rotors/motors clearly seem to be the future. No drive shafts. No gearboxes. With appropriate design, a much higher degree of failure tolerance and safety. Improved authority. Less noise. Less maintenance. With proper engineering, what's not to like about it? A bigger alternator, a small battery backup, a two channel control unit, and none of this is rocket science anymore.