Sounds like a mix of these and buck in the magazine would be just the thing. If the goblins are wearing body armor, then the flechettes' will penetrate, but if they aren't the buck will be a better stopper.
But which to put in the chamber for that first round? I'd lean toward the buck, because even if you don't stop 'em with it, you probably slow them down enough to get in that second round of flechett, should it be required, and you might get luckey and hit an extremity, like the head, with one of the shot.
What are others' thoughts on the matter?
I Dutch load. First round lots o' small pellets, to increase chances of a hit, subsequent rounds fewer larger pellets to penetrate denser cover as the perp trys to get in a better position, I end up with rifled slugs.
I didn't know flechettes were available to mere mortals like myself...