Reshuffling doesn't take up a whole lot of time. You just aren't mashing R2 fast enough; and yeah, because I want to watch my characters do each and every single hit without Quickenings, Quickenings DEFINITELY takes up MORE time. As for the speed, yes it does help, because if you are attempting a challenge, I seriously doubt you have any problems with finding the D-Pad.

As I said, if you think you can do it, go ahead. You aren't really going to convince me it can be done until you do it.