Where I find these DoF calculators begin to break down is in the area of lens quality and sensor pixel pitch.
Ray, it's just that "DOF" is defined
Historically, DOF has been defined by using the 'perfect lens' formulae and a 1/x ratio of diagonal format that matched both an "acceptable" quality for viewing print AND the resolution of film used at that time.
Resolution of lenses and films and then digital cameras has improved, but this hasn't changed DOF definition... and for good reasons: simplicity, relationship too Out Of Focus Blur and probably the most important one => photos are meant to be viewed, not to be scrutinized with a microscope at 100%...
That's why we keep finding it in most litterature and in all online DOF calculators. This is also what is used by all manufacturers (Canon, Schneider, Leica, etc...).
Using a different 1/x ratio of the format depending on one's needs is still within this definition.
Taking into account the Lens resolution, Sensor resolution, Diffraction, more accurate formulae depending on lens design, non planeity of focus area, whatelse... is a different
Anyone can use and refine such modelization if they want.
The only thing I am asking is to use a different name than "DOF/Depth Of Field" which is assumed to be the traditional definition (and is really mainstream)
in order to avoid misunderstandings. This is why I suggested "Useful DOF", etc... for those different concepts.