Logic often works well. If the revised OCA(H) is below the DA, you will be safe.
I worked on compiling minima for a major chart manufacturer. We would take the OCA(H) from the State's AIP, stick it in a computer programme and calculate the CATI & II and minima. IIRC the actual DA was usually about 10% above the OCA(H) and always above the regulatory minima.
CATIII approaches obviously require a different system because they're based on the nature of the undulating terrain on the approach. I can't remember the details, especially at this time of the night.