Uhh, Bloodlines has absolutely fantastic writing
No, it was okay, but surely not fantastic. But then again, Bloodlines also put additional emphasis into the actor performance, I thought that contributed also to the personality of the NPCs. In the end, it's not purely the dialog quality that makes or breaks an RPG these days, but how well all parts (acting, VO, design, functuality) play together that make it a satisfying experience. And I think if I can survive some badass dialogs a'la Gothic and still can enjoy it, DA should be a diamond among good ol' fashioned RPG goodness.
I can't think of single badly written character in the game. Jeanette, Prince, Anarchs etc. were fantastically written. Even minor characters like Fat Larry (best. shopkeeper. ever) and that japanese demon hunter had a lot of character in them
Storytelling ranged from average to utter fail, but that's not writings fault.