Serene Guardian - Shattered Gates of Slaughtergarde
You can enter at level nine, and it'll do half progression on your flurry, AC bonus, and unarmed damage. You might want to delay entering for a level to get improved evasion - your choice.
Full BAB, good reflex and fort saves.
The resonance abilities are decent (though, to be honest, resonance is much better accumulated by rapid-chucking splash weapons). The fact that resonance points never go away is useful for dealing with recurring opponents, and your special abilities don't have silly per day or per week restrictions.
Most of the resonance abilities are mildly useful, but one in particular is incredibly good.
The eighth level ability lets you spend a swift action to bestow no-save confusion on anyone you have hit multiple times in a round. If you can't do that with a BAB of 14 at level 16, you're hopeless. The duration is very low, but hey, it works at any range, and it's a 70-90% chance of wasting an opponent's next few actions (or even better, turning them against their own party).
Either way, it makes flurrying shuriken almost useful. DR will still kill you, though, so keep a supply of different energy splashes as backup just in case. I'd recommend liquid salt (sandstorm), since practically nothing has dessication resistance. I'm sure the party caster can hook you up.
Of course, a full BAB guy could enter earlier, and replace the partial monk progression with a fighter bonus feat.