Actually not that great for DNC since they have Charis Feather (DEX 5, increases critical hit damage 5%) which is also a 100% drop from ironclad executioner.
Also from what I've read, the critical hit bonus is only 5%
I agree that this would probably be a good Blade: Jin piece (depending on how much damage it adds to crits), however I think this piece is really meant for a NIN using Innin.
@khimaira
I think isn's that easy, dual wield is only good for dot, foe will gain more tp and u still gain more or less the same, this will add u a 3-5% dmg to all your crits(including SA and TA), that is a good bonus when u put along with RR or other crit amta plus equipment. I don't really know what is best cause with more hits from raider's boomerang u will trigger more crit hits, will be nice if someone can do a test. i hope i explained clearly :p
I have one for my 85 nin and its absolutely nuts with Razed Ruins atma. My jins are hitting for 2k+ or so in abyssea and my WS set isn't top notch, though its at the very least, decent.