There are certain quests that can be failed due to player decision. And there are a couple exclusive quests for players that choose a certain path. But you have to realize that those decision can only apply to that specific quest. If that quest decision impacted multiple quests or NPCs the game would have to fork or players would be left out of multiple hours of game time. There are a couple NPCs that won't speak, are rude and up charge you, or do not become vendors depending on your choices. Even making all NPCs or a large group of them respond differently requires that they dub more hours per dialog. Keep in mind, the characters in D2 appear more round because they all have at least a couple of lines that are randomly spoken.
The amount of gameplay hours is what makes D2 great. So let's make is a little poll... What would you rather have: more hours? more impactful decisions?
IMHO, the developers thought the former was a key priority. But if you do not, let them know.
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EDIT: I'll comment on the class specific quest. If I remember correct its something that has been brought up before but it's an element that wasn't implemented. Maybe you'll see it in future games.
Last edited by candlebbq; 04/02/11 10:04 PM.