I doubt anyone could feel the 6-8W of a dyno hub of 3-5 watts of a Rohloff hub. Imperceptible doesn't mean irrelevant
I am a low power, efficiency minded rider.
On my last 600K, my moving time was 22:39 and my average power was 89 watts (102 normalized) for the whole brevet. If I lost 10 watts due to any frictional source and that is not hard to do, the ride would have taken me about 1.5 more hours moving time. Everyone weighs a different amount and presents a different profile to the wind, so, YMMV. On a 1200K, this becomes 3 hours extra time. This is on a bent. Real numbers. I would have to really dig to find my power numbers on an upright.
The above example is I think the point CFBoy and I are trying to suggest.
WRT pulleys, anything but the top of line derailleurs usually have bushings instead of ball bearings. Replacement is an easy 1 watt. They are also easier to maintain. I use Hawk Racing steel bearing pulleys....they are close enough in performance to ceramic but a fraction of the cost. I also use their BB. I use NTN low friction bearings in all of my wheels. A watt here and a watt there eventually adds up. If the Rohloff were truly 2% less efficient, that is a lot of wasted energy for this old bag of bones.