Just how does conditioning mono H compare w/ LANTR (LOX Augmented Nuclear Thermal Rocket) concept ?

The purposed are different.  LANTR lowers Isp but greatly increases thrust over basic NTR.  It is still way about chemical Isp's.  The concept of using electricity to produce monatomic H increases Isp above basic NTR. 

The difference between the LANR and the nuclear rocket with electric disassociation of hydrogen to monatomic is both in technique and purpose.  They are the same in one respect and that is that they start with a solid core nuclear rocket and they both augment the propellant flow before it leave the nozzle.  There is a big difference in that the LANRs augmentation is designed to increase the thrust by injecting LOX to burn in the propellant flow.  This releases chemical energy into the flow while it also increases the average molecular weight of the flow.  The net result is a lot more thrust and a lower specific impulse between LH2/LOX chemical and nuclear thermal.  The lower specific impulse is due to the higher propellant particle mass. This is useful to increase the thrust to use in application such as getting to orbit.

 
What I suggested would be to use an electric current after the flow is entering the nozzle to disassociate the hydrogen into monatomic hydrogen so that the particle velocities would increase at a given temperature.  Since specific impulse is proportional to the square root of absolute temperature divided by the particle mass this can increase the specific impulse up to a limit of 41%.  This concept would be for use in space leaving and beyond LEO.  This concept doesnt require massive increase in propellant, i.e. LOX like the LANR does. 

 
My motivation was Dr. Dewars Ninth Generation System in which he discussed disassociation of hydrogen.  On of the points he make is that the propellant flow is on the threshold of this anyway.  I though that an electric current might be a practical way to push the process.  He mentioned lasers but I dont see how to apply them at the place where would need to be done, i.e. in the annulus of the nozzle.