Warning: spoilers

I have not started nwn2 yet so i can't really help you with this one, but I like the topic overall so I will participate :)

In sotu and hotu there are many examples where being evil has some profits. For example: in hotu on first level of undermountain there's a war between pixies and ogres. If you fight their leaders they will ask you to spare their lives and if you do, you don't get any profit for doing so. No exp nor items. But if you're evil you can kill them both, get a lot of exp point and good loot from their corpses.

But overall I think that it's difficult to fit evil character into world-saving plot and a lot of dungeons and dragons based games are about saving the world. Money can always be used as the reason, but for how long? Real evil character would ditch the quest at any point they feel the risk is too big to be worth it and i guess it would come to their minds rather quickly. But actually sotu and hotu kinda resolved that problem: you can say that your character is starting the quest for money and after some point in the game is forced to do the rest, because this is the only way. In sotu you may want to just take revenge on the final boss for what she did to you. In hotu you literally can't escape so you have to play by the rules.

In case of torment, I guess the good way is actually the only one. Throughout the game you get to know all the things your character did and those things were mostly bad. The whole thing is about to get some kind of redemption and the finale is really satisfying if you manage to fight nameless one' bad side.

And there's also a quote from wikipedia:
"Bill Slavicsek and Richard Baker's Dungeon Master For Dummies noted that a party of good or neutral characters works better as the motivations for adventures are easier, the group dynamics are smoother, and the "heroic aspects of D&D shine through in ways that just don't happen when players play evil characters"". [url="https://en.wikipedia.org/wiki/Alignment_(Dungeons_%26_Dragons")]Full article.[/url]

So as I said, being good actually fits the whole thing about saving the world and being a hero, so long term goal is not really fitting evil characters. But the short ones might still work, for example killing everyone you want to kill just to get more gold after finishing the quest.

Also, you said about disadvantages, but what are disadvantages for evil character? Loosing all your friends? What friends? You are evil, you don't have any friends, you may need them to fullfil your goals, but then what? Just kill them or leave them - this is what evil ones do. This of course may and will lead to everyone turning against you at some point but this is what you asked for.