Dianne Leong DBs attack real fast so the the safi set bonus procs faster than most weapons. (The set bonus makes you lose health for a certain amount of hits and then recovers it). Hope i helped you :)
You can figure it out in the arena when the monster is down or paralysed. If six fold slash then demon dance then six fold again and then dance again does more damage, you go that route. Else try out repeated blade dances when the monster is down and see how many blade dances you can cram in there. I have been a dual blade user since the beginning and I usually prefer this- six fold slash, followed by two demon dance. Because almost always a third demon dance never connects completely.