Short answer - no. As the reducing valve has a vent open to atmosphere. So the reducing valve outlet pressure will also change slightly as well with atmospheric pressure changes.

Dripping sometimes is most commonly caused by thermal expansion as the cylinder reheats. Next time the valve is dripping, switch off the power to the cylinder. And see if the dripping stops.

Normal amount of water discharged is around 1% of your hot water usage. Note that if your roof is coloursteel, that dripping will damage the roof.