I have only owned and shot the Fosbery/Paradox system. But since you have said it I will offer that everything I have read and several conversations I have had with the industry people who would know support your statement. That is, a system that successfully fulfills BOTH roles as bore rifle AND shotgun. It should come as no surprise that the various ball & shot systems were quickly abandoned when the H&H Paradox (Fosbery Patent) patent expired and there was a rush to copy the H&H system. I did not know Rigby had made so few. Holland & Holland has made ~1500 over the years and is again cranking a new one out now and then.

That said, I would still expect to see Dutch's Colindian cut a group on paper at 50 yards and, after reading the tests in Shooting The British Double Rifle, to print a decent shot pattern at 30.