I sight rifles at the indicated POI for point blank range for the load and rifle I am using, for big game. My 25-06 is 2.5 inches high at 100 and 3 inches low at 320 yards (3 inch vital radius). That way I don't get to guessing on hold over etc. If it looks long--and my judgment can be poor on distance to mulies and speed goats-- then the point of aim is "a couple of inches below the highest hair on their top line." If they ain't aware of me and I can fumble around and get the range finder out and use it, then a better estimation of hold over is possible.
A guy I know shoots bench rest and long range shooting, and he zeros at 100. He is more into the technical aspect of figuring trajectory than me.