Not sure if it's only me, but as far as I can see, most of cutscene dialogues don't have voice acting. There are only a few important cutscenes have voice acting. Is that normal in this adventure pack?

From what I've seen of LP's, yes. But to make double sure, check out an LP and go through the cutscenes you've already had and compare them.

'Let's Play'. They are all over YouTube. And yes, the lack of full voice acting is normal. NWN is not an interactive movie scene type of game, like Mass Effect.

Imho, so many cutscenes lack voice acting affects the quality of the game and is a bit disappointing. The original campaign and MotB have voice acting in all cutscenes, don't they?

Most cutscenes, not all I think. But not all modules -- even premium modules -- had the resources available for full VA. MoW is not the worst in this respect. Even in games like Mass Effect that rely very heavily on voice acting, DLC, more often than not, is inferior in either quantity or quality.

I see. Thank you.