The problem with having completely predetermined stories is that I seriously can't be expected to predict the course of the entire game before it even begins! And then with the paragons being random and all, I wouldn't really get to even design them. At most I could do one quest for each faction (that is, for their warlord), and that'd be incredibly boring, right?
Anyways, what I had in mind with the adventurers was more like this: there are adventurers that travel around the land on quests, going from town to town and such. The adventurer doesn't always pay allegiance to any god, but he usually won't be hostile towards any, either. Now, if you find out an adventurer is passing through your city, you may want to seek him out and through a bit of coaxing learn what he's doing. And when you find out what the adventurer's quest is, you can help him out. Then you get to help him on his quest and hope for a reward.
Sometimes the adventurer is looking for an artifact, sometimes he may be working on doing something for an npc state, sometimes he may be sabotaging an npc state. Depending on the outcome of the quest, you get different rewards, like the adventurer joining your faction as a paragon, or perhaps the adventurer will share some long lost knowledge he's found on his adventures, or maybe you want to double-cross him and steal the artifact he's been hunting. I want the player to have a lot of control over the outcome.