too mild camshaft

Sorry but a higher ratio rocker does affect duration at .050 a little due to bringing the valve up to .050" lift quicker. It would also have to affect the total duration since it's rate of lift is faster. Although it is so minimal it probably wouldn't be noticed.
It would still have zero effect on the duration figures as measured at the tappet. It only changes rates on the valve side of the fulcrum.