Actually, there is some good information that can be obtained from a plot of SWT vs U*R(g). Testing is usually done at 100 km/h. Presuming that you can get a decent statistical description of the Steering Wheel Torque gradient (N-m/g) at 0.0g [TG0] AND a decent value for the Steering Sensitivity (g/100 deg SWA) at 0.1g, [SS.1] then a metric referred to as the "Steering Work Sensitivity" can be computed from 57.3*SS.1/TG0.
Values for typical passenger cars lie between 2.5 and 3.5. Anything out of this range is a bit out of place. High values (lets say 3.5 to 6 are twitchy or darty and too "light" fot the amount of steering gain the vehicle has. It could be too much power assist or too much steering gain. Vehicles with a work sensitivity below 2.5 are too "heavy" (not enough boost or not enough steering gain. Across the board, manufacturers typically produce sports cars that are NOT in the 2.5 to 3.5 range for various reasons. Manual steering, heavy parking effort, understeer is very low (meaning the gain change with speed is high), a very quick steering ratio, difficulty in blending low speed steering boost with high speed assist, heavy tierod loads, very light tierod loads, marketing image and the cost and availability of special steering gears, valves and pumps and good tires, blah, blah, blah, hopefully you get the idea.
But the cars (and trucks) that are the most fun to drive (nimble, sporty, easy, etc, have work sensitivities in the 3 to 3.5 range. Given this basic relationship: (there is an appropriate steering effort buildup for a given level of maneuverability) the wheelbase of most cars (2700 mm), the understeer of most cars (3.0 deg/g) and the steering gear ratios of most cars (16:1), you can quickly figure out what the boost rate for a good steering system ought to be to drive comfortably on the highway and get good ratings for it from MOST drivers). The engineering required to get an appropriate tierod load gradient (N/g) and a pump flow rate and a valve profile to deliver the parking effort and a means to roll the assist off as you pick up speed is where all the artistic handwaving (and a good simulation) begins.
Been there, done that.