Err..., you're not doing more of the same, because each character is different. You do some things with a fighter, others with a cleric, others with a thief, and so on. So in a game with more characters, you have to decide where and how to use each character differently, thus adding a whole new level of decisions you have to make to vanquish your enemies. On the other hand with just one character, like, say, a fighter you have in NWN1, what. four options? Knockdown, power attack, called shots and regular attacks. And that's all. For a whole 20 to 30 hour game.
The orcs were easy, no argument there. But I had more fun with them than in other encounters in the game. I think it was the wide open spaces first, and later the orcs spawning behind your party, IWD2 style. Just gave me more things to do.