What difficulty do y'all play on? I usually play rpgs on easy because I like the exploration, reading, and dialog more then the combat, but some points in the NWN OC and the boss at the end of Underdark gets crazy hard.
I just kept dying over and over, so I had to turn on on god-mode at these points. But why where they so hard?
Was it something wrong with the way I played? or is the end battle of the OC and Underdark known to be broken? And if they are bananas on easy, how do people on harder difficulty manage to survive?

i've never played nwn that long, but it might have to do with unoptimal character builds or the fact that you don't control a party. still, normal nwn has some forgiving aspects to it (no friendly fire in aoe spells for instance)... you have to plan things carefully and check with abilities/spells you're using.

I finished the game and the expansions on very hard without any problems using Sorcerer class. You have to carefully plan your character, select the appropriate feats, spells and so on. What class are you playing?

I made a ranger for the OC, and used my cleric from Undentide in Underdark. In the OC I got stuck at the two dragons and used god-mode from that point on, and in HoU it must have been a bug or something because my dark-elf companion (Nirra?) would just stand there and not attack. So instead of trying to get her to behave I just got frustrated and bored and turned ot GM.

There are a couple of tough fights in Hordes, but you also get to craft +10 weapons with elemental damage, and that final boss fight can be avoided if you have extra money to spend before you get there.

The only real challenge for my Sorcerer was the final battle. I didn't have enough spells to bypass the boss immunity to elemental damage. Luckily one of my followers had armor which caused divine damage. I wouldn't finish the game without this. :)

That might have been my problem, I horded my gold and din't invest in anything, just upgraded my weapon a little bit. General question but is a +10 without bonuses better then a +8 weapon with elemental damage and other bonuses?

The OC has some wildly imbalanced bosses with frankly ludicrous stats. Thugs with more hit points than actual dragons, low-level spiders with poison so potent as to virtually incapacitate you if you're struck even once, ridiculously high-leveled wizards throwing out spells that should be able to insta-kill you in all rights, you can easily get screwed over and the only reason it's tolerable is the free auto-resurrect.

Hordes of the Underdark is much better, but still has its fair share of tough fights. I don't know which ones in particular gave you trouble, but often times those battles have ways to exploit them to make them easy. The Valsharess in particular is a pushover if you have access to dispel magic, as she's entirely dependent on her magical buffs and is completely helpless without them. What was your strength score like? Rangers need very high strength scores, otherwise their damage will be too low to get much headway. Odd that your companion was bugging out, but did you not have any means of dealing damage yourself? High-level Clerics are incredibly destructive both in melee and with spells. It really depends, both on your character build and the specific enemies you're up against. As a rule of thumb if you need more accuracy in order to hit enemies consistently, go with the higher enhancement bonus even if it doesn't have special properties. If you're hitting just fine, but aren't dealing much damage, then the special properties will be more useful to you.

For NWN/NWN2 I play on Normal difficulty. Under normal circumstances I prefer to play on Core rules for D&D games, but the party AI and interface for the NWN games just makes it too difficult to keep party members from wandering into my AoE spells (I primarily play casters) and it's SUCH a pain in the rear.