I was able to solo these (one on one) by the enterances as a lvl 40 SAM. They have a special that's like Edgar's Bio Blaster from FF6, I recommend highly you watch for that.
This looks like a couple of people I've partied with on Leviathian. If so, how's it goin'? As far as these guys go, I've only fought one and it didn't drop any items for me, but I do know that Moblin thread has been gradually declining in price.