I have not played NWN2, but I have played the original Witcher. The Witcher enhanced edition is the same game, with more dialogue, tweaked combat, etc.
It’s an action RPG with a heavy emphasis on story and dialogue. I would say about half the game is combat, and half is running around talking to people.
Quests:
Most quests are pretty complicated, there’s none of the “go here, talk to guy A, go there and talk to guy B, quest done!” stuff. For example, there’s a huge “detective” storyline in the 2nd or 3rd chapter that’s going to take talking to dozens of people to solve a mystery. Depending on who you talk to and what you say to them, there’s at least 4-5 different endings to the quest, and it’s going to take a couple hours minimum. I was doing other quests in between, so it took me about 10 hours for the whole chapter IIRC. There’s a ton of sidequests, and most have more than one way to completion. Very nice change of pace from the usual fedex quests, and definitely one of the high points of the game.
Combat:
Combat depends on different styles to deal with different enemies. You choose between group, strong, and (forget what the 3rd style is). You can easily switch between different styles on the fly. There is a rhythm based clicking, time it right and you do much more damage. It’s very arcade like and fun, but it does get a bit repetitious late in the game. It never got to the point where it was boring though.
Items:
Sadly, you won’t find a lot of weapons and armor in the game. I think I only used about 3 different swords and 2-3 different armors in the whole game. You can pick up different items from the baddies you kill, but they’re not as good as your Witcher sword so they usually just get sold to the shops. A bit disappointing, but not really that big of a deal overall. Just be aware this isn’t a diablo type item fest where you’re constantly finding new weapons/armor/etc.
Magic:
You have to make your own potions from plants, bits of monsters, and other stuff you find. Fortunately the game makes it pretty easy to do this, with recipes listed on the mixing screen. The potions serve instead of inherent magical abilities, and can let you see in the dark, enhance your combat skills, etc.
Storyline/Characters:
This is one of the strongest areas of the game. Every character seems unique and has their own personality, and is very memorable. The dialogue is all voice acted (with subtitles if you wish), and it’s pretty interesting. I would say the story and characters go far beyond the bland, generic stuff you see in many games, and more than makes up for the somewhat weaker areas of the game.
Skills:
By endgame you’ll have points in almost all the skills, meaning you can’t really customize your character. Since your character uses potions in lieu of magic, almost all of your skills are combat related.
Graphics:
I played the Witcher last year on my old PC, but I thought it looked pretty damn nice. NPC’s will scurry under the eaves when it rains, you’ll catch little bits of their conversations with each other about how they forgot to bring the washing in or whatever. Impressive weather effects, nice character models and animations, nice graphical effects, etc.
Summary:
(Keep in mind I haven’t played the enhanced edition yet, so I’ve no idea how that changes the game)
The Witcher has a fair amount of combat, but you’ll spend just as much time talking to people, and even some time standing around watching the city scurry by. The game plays like an interactive novel, and I mean that in a very good sense. Great storyline and quests, easily among the best I’ve seen in a RPG. The downside is the weak collection of stuffage (few weapon/armors/powerful magic trinkets to be found). The game is pretty varied and interesting, very different than most RPG’s. The city environments are as much of a character as the rest of the game. This is likely to be about as different from NWN2 as you can get, but I’d highly recommend it.