So in short, she'll be useless at offensive magic, and to even get anything possibly usable out of defensive, I'll still have to respec her to fix her spells. The news is now getting worse and worse.
:(
I have the DVD release of NWN Diamond installed, and had hoped to play through the OC and earn character level 40 by the end.

So it comes down to some respec work to turn her wizard stuff into defensive only since she'll be useless at offensive, or respec her turning her into a pure rogue, or my PC catches the Wailing Death and I restart the game from scratch, choosing an entirely different class, and across the board I have to forget about earning character level 40 and the Epic class levels.
Real fun choices. not.
:(

As we speak I'm about to start the Blacklake PETA memorial mission (Having done the short raid on the tomb and the wizardlab); After that, Meldanen, and some obvious plot hook I don't remember from before about a butler drafted into to houseguard, and rescuing a senior guard.

Forgotten Realms PETA - Remember, if the woman you love gives you poison Ivy in uncomfortable places, she may not actually be a woman.

You don't need to respec to make the wizard defensive. Just buy some more scrolls and learn different spells.

But like I said, potions are better than the spells you get, so you're much better off scrapping the wizard levels altogether. Or indeed restarting.

If I may make a suggestion: Fighter/Rogues are fun multiclasses. Ranger/rogue or barbarian/rogue also works.Those classes add hitting power and survivability to your rogue, whilst the rogue levels still let you do all the fun stuff and let you use spell-scrolls and wands with the Use Magic Device skill, so you can do a bit of everything. Your way of having about 4/5ths rogue levels works very well for them.

Here's another option: Play the expansion instead.

You can start another level 1 character in Shadows of Undrentide, using what you've learned of play so far, and play that. It's a pretty good option: SoU is rather more fun than the OC, and afterwards you can use the same character for Hordes of the Underdark which is by far the best of the lot and will get you (some) epic levels.

The stories of these expansions are unrelated to the one in the OC, so you won't be missing out on anything. You can always come back to the original campaign at some later date if you really want to.1

And if you really want to reach level 40, you can then install some user-made continuation modules that will let you take the character on further adventures. Though honestly, I think the game is the most fun in the level ranges up to 25, i.e. the range you reach in HotU. Afterwards, characters cease to really gain much in the way of interesting stuff and it's just more hitpoints, more +1 to X bonuses, etc.

If you are planning to mostly spec Rogue, then I strongly suggest taking a one level dip in Shadowdancer for Hide In Plain Sight. It can make rogue life SO much easier in several ways, from sneak attacking through out a battle (on things that aren't immune), to taking a "time out" if the fight is getting out of hand.

I wouldn't go further than 1 level in Shadowdancer, but that single level dip gave my (otherwise single class) rogue massive amounts of extra power.

I'm still trying to decide if the Darkvision is worth it for level II - I don't *notice* much difference, but then i just means I have two more hitpoints and two less skill points. Worth it for a human or not?

I don't think it is worth it. A quick search online indicates that Darkvision will negate a very specific kind of Spot check penalty -> -5 to Spot if it is night and you aren't using a torch. I never used a torch much anyway, and your rogue's spot check should be plenty high enough to not care about the penalty.

Out of curiosity, why human instead of elf, if you are using a rogue? The biggest elf feature for me was having Detect Mode automatically on, all the time, with no speed penalty. You can sneak and detect traps while still going half speed (or full speed with haste boots).

Indeed it is not. Darkvision is completely useless. For one thing, in the OC you hardly ever need to make any spot checks in the first place. (Hardly any enemies use stealth, and finding traps uses the Search skill, not the Spot skill.)

If nothing else, as a wizard you can cast Ultravision which at least lets you see through the Darkness spell. (This is a very good combo for wizard-rogues, as you can cast Darkness yourself and then get sneak attacks on all enemies who can't see you, whilst you use Ultravision to negate the miss chance. But you do need to have a decent number of wizard levels, or the spell won't last long enough for it to matter.)

Note that if you take the second Shadowdancer level you're not just missing out on the extra skillpoints, but also slow down your sneak attack progression and your Rogue bonus feat progression. A rogue 19/SD1 gets 10D6 sneak attack and 4 special bonus feats, a rogue 18/SD2 only gets 9D6 sneak attack and 3 special bonus feats.

Taking a single level of ShadowDancer is indeed very powerful, but do note it can mess up your attack bonus progression. This is mostly relevant for the fighter/rogue class I mentioned above. If you're a rogue 16/fighter 4, you get 4 attacks per round. As a rogue 15/fighter 4/Shadowdancer 1 you only get 3.

As you can see, multiclassing can get quite complicated quite fast in NWN.

How does Hide In Shadows differ from Invisibility (beyond skill checks being needed to maintain HiS, instead of a second level arcane spell slot)?

If they are virtually the same, I'd be inclined to take Invisibility as an At Will ability over a 4th attack, I think.

For most intents and purposes, if your skills are high enough stealth is just as good as invisibility.

Hide in Shadows/Move Silently slows you down and requires skillpoints and doesn't give you the concealment bonus. However, (though this is only relevant in multiplayer) skill-based Stealth actually hides you even if you move right next to another player, whilst invisible characters will appear as a shadowy outline when they do so.

In general, HiPS is extremely powerful and a level of shadowdancer definitely helps a rogue. (Even if you do also need to take a couple of otherwise not terribly important feats.) My point was more that it helps to understand how base attack and such work and to make sure you're not surprised by such things.

For example, you could have both Hide in Plain Sight and that fourth attack by taking 7 fighter levels instead of 4, or by delaying taking Shadowdancer until your 21st level.

That fourth attack might not seem THAT important, except because of the way sneak attacks work in NWN having 4 attacks means you get to sneak attack twice when coming out of stealth, instead of just once. If you have four attacks, dual wield for 2 more attacks, and have Haste from an item, you even get 3 sneak attacks. Getting more sneak attacks obviously benefits a rogue quite a lot.

Oh, On some level I think I still associate humans and demihumans with different types of muticlassing. It's a good day when I don't calculate THAC0 - <G>.

Okay, I hate to respec again, but if Darksight has that little effect, I may say the heck with it and do my last level over. I almost hate to take Shadowdancer at all if it's only the one awesome level (although Hide in Plain Sight *is* in fact awesome). On the other hand I saw no other appealing third classes, so ...

Sigh.

Ah, fair enough. I don't usually worry about stacking multiple sneak attacks in one round, because I run up (while stealthed) and poke the enemy, then take two steps back to Hide, and rinse and repeat. Life got so, so, so much easier when my rogue finally qualified for shadowdancer, and I'd happily sacrifice the fourth attack to have HiPS much earlier.

Just checking. Depending on the circumstances, a human may have still been the "right" choice, but it didn't seem to offer anything beyond what an elf would in this particular set of circumstances. Wizard is the elf's preferred class, and prestige classes don't trigger the multi-class xp penalty. If you wanted to mix fighter, rogue, and sorcerer, you'd definitely want the human over elf unless you were keeping them all even.
If you are going rogue primary, and you don't need that 3rd "class slot" for anything else, then take the single level of SD. Don't bother with SD 2, but HiPS simply is that awesome for a rogue.

Dance between combat and shadows, and enjoy it! :D

Yeah, me too, actually. It's more fun to have a character that can do neat things early than it is to get strong very late in the game.

There is no reason that taking SD has to sacrifice that extra attack.

The rule when talking medium BAB classes (like Rogue or SD) is to take them in blocks of 4, or fill in the missing ones from a fighter type class.

So you can do:

Fighter 4/SD 4/Rogue 12
or
Fighter 7/SD 1/Rogue 12

Both give you the same attack bonus and 4 attacks/round.

You do sacrifice Sneak attack damage.

But if you now getting in 2 attacks out of stealth instead of 1, you will still be doing more sneak attack damage.

1 x 10d6 sneak (max for a full pure level Rogue 20).
is less than
2 x 6d6 sneak multiclass Fighter/SD/Rougue.

Also you will be much better equipped to handle the sneak immune, which there are plenty of.

I would never give up 4 attacks/round, they trade-offs are not worth it.

-When your attack pattern consists of "poke-backstep-hide", you don't get much benefit out of those extra attacks that you aren't waiting around to take. You are stabbing an enemy, then immediately backing up and hopefully hiding before they get a chance to swing back. Standing around for an extra attack or two (or three) invites damage from attacks or spells.

-You only get that "extra" sneak attack damage if both of your attacks hit.

-I'm not sure what extra bonuses those 3 levels of fighter or SD are supposed to provide; see above about my response to picking up a fourth attack.

-Last: You are right, in that a 20th level character doesn't absolutely need to give up that 4th attack. If you already start at or near level 20, then you might consider building for it. However, when starting at level 1 (OC, SoU), I stand by the idea that having Hide in Plain Sight by ~level 8 is far more advantageous to the character overall than building to get that 4th attack at level 20. And if I had to pick between them, I'd take HiPS almost every time for a rogue primary.