You want Pistols over Dual Wield. If you can fit Dual Wield in to trigger Defensive Opportunity, cool. Yet, Pistols triggers Offensive Opportunity, and you really want that.
Shinobi-Iri buffs all your defenses. Fully enhanced, it isn't a lot, but you can squeeze nearly 2% more out of it. It adds up for /Nin which doesn't hit 45% as easy as /SR. Shinobi-Iri puts you into stealth and it suppresses when combat starts.
I prefer Kemuridama for a toy over Blinding Powder. Kemuridama is placate which is kinda neat. Blind Powder, Misdirection and Kemuridama is overkill. Pick one.
Bo Ryaku is worth enhancing a little or using for set mules.
Otherwise, the presented build here isn't a bad start.