Actually, I have never really had much issue with that thing but yeah, the damage reduction it has could be annoying. I would recommend first taking Daelan down with you - he does enormous damage and can take it out pretty easily. Depending on what class you are, I would look into other options, such as a wand of magic missiles (ignores its damage reduction), scrolls, etc.
You *could* try a better weapon, since the shortsword is kinda pathetic really, unless you're dual-wielding them - really, leave the shortswords to the rogues and halflings and get yourself a real blade. Frankly, getting yourself the hurtiest sword you can (a greatsword) would be worthwhile, assuming you're playing a fighter-type. Optionally, you could go for a scimitar or rapier. While the damage is still 1d6, they crit on an 18-20, and it's crits that are going to really make that devourer go down.
What class/level are you? Hard to give decent advice without knowing the specifics...
