Well, it's a tough poll, Xillix. We don't want to flood the writers with tons of material that isn't really necessary. And I'm not sure beyond what is basic and everyone knows already they should talk about. The writers are already writing the quests, the lore and history of the world, they would be the best people to know which NPC's should say what.
I think maybe the best way to answer this would be to describe how the perfect NPC would be created, so kind of building up an NPC to deal with questions might go something like this:
1. Develop the quests for an NPC, and supporting dialogs. One thing that I've been somewhat frustrated with is that they don't seem to know much about their own quests, so at a minimum, every NPC should be able to answer questions related to their quests (which is why we, the players, need to send the writers our top 10 questions as we get them).
2. They all should know something about the stores and vendors in their general area.
3. After that, build a family for each NPC with a story board for each of them. Ask the question, who would know who in game, and if they know each other, then answer questions about them. Every NPC should know some other NPC's in game, and in the size of the cities in game, many of them should be related in some way.
4. After that, build up their feeling towards topics. Religion, Economy, Politics... the big three we aren't supposed to talk about, but everyone does.
5. Then add in fun things, random sayings, etc... as much as time will allow.
I just laid it out in a way that you could develop as much as time allowed. Don't know if that's a better answer, but the only way I can really think to address it, and maybe it'll trigger some better answers.
