I noticed the same thing about velocity running through the revolver. Much more difficult and it tends to bind up more. I switched to the kong robot instead of using the revolver/ figure 8 set up and it's great. Very smooth, easy on/off and no binding no matter what rope I'm using.
I'm loving this set up. I've been using for a month straight, no drt, no unicender, just the robot, hitch climber, a piece from Rich hattier's anchor bridge and 10mm ocean polyester line. Great set up. Can't wait to get my unicender back to incorporate it into the system (not having to safety in to hook up ascent mode is going to be a huge advantage)