*coughs* Do, ah. Do you have weapon finesse? Because if not, you're using your strength score (13, so +1) instead of your dex (18, +4) for to-hit calculations. It'd make a difference. Can't recall if the dual wield feat you're talking about helps mitigate that penalty to using an offhand medium weapon, too -- you might try swapping the offhand rapier for a dagger or somethin'. Nix that, I just noticed you said you were offhanding the shortsword, which should be fine.
Beyond that, if that weapon description is entirely accurate, those are +0 weapons with a neat bonus -- basically they're not helping you hit things at all. And beyond that, I'm pretty sure I remember NWN having damage reduction, which may mean you're trying to hit things with them you very literally can't damage with those particular weapons. Though checking, the daze version for both is +1 -- still not helping that much, but more than nothing. Don't remember what enchantment level was normal for that part of the game, but I'm fairly sure a level 8 character should be at like +2 or 3 at a minimum, if my memory's not completely shot. Also probably want to keep an eye out for +dex items, as that'll help your accuracy if you get finesse (alternately continue getting strength up). Add on some basic buffing (Bless, cat's grace, etc.), and you should start hitting significantly more often.
Basically, if that half-orc is using a +3 or up weapon* and not dual-wielding, has high strength, and is a higher BAB progression class (fighter, whatev'), it's definitely going to be hitting (a lot) more than your rogue/assassin dual-wielding +1 weapons and pinging its to-hit off its low-ish strength instead of its high(er) dex.
*E: Ah, and can't forget any weapon specialization feats it may have. That can be a few more points of accuracy, iirc.
Also, I'm like sixty percent sure you can turn on more detailed roll information one way or another. If you can do that, it'd make it a lot easier to see what's going on.