I've built but have yet to play:
Swashbuckler 3 / Fighter 2 / Dervish 10 (perhaps Barbarian 2 in there?)
Feats: Finesse (from Swash), Wp Focus, Dodge, Mobility, Expertise, Two Weapons (and Improved and Greater), Spring Attack (from Dervish), and Improved Crit.
Assuming you can get a 16 dex and int to start (and spend points on dex later)
At Level 16:
+27/+27/+22/+22/+17/+17/+12 1d6+8 15-20/x2 while moving 45 feet (more if you take the +10 speed feat from FRPG, or the Quick trait from UA, or Barbarian). And it lasts 9 rounds (assuming you're smart enough to keep Perform: Dance maxed, another reason for the high int).