I assume the drag is from the Nexus 8 using roller clutches instead of ratchet pawls?

The Dahon Curl D9 (hyped but seemingly available nowhere) spec'ed a 9 cassette, and the derailleur had 3 rollers and not just 2, the 3rd roller on the end of an L-shaped cage only engaged when the cage was well aft on small cogs, to take up more slack, without a longer cage reducing ground clearance.