I'm on PC with the deluxe edition, and my friend on PS3 has the deluxe edition as well, she's also reporting this bug. Anybody without the deluxe edition getting the bug?
I just tried playing for a bit, went through the Hissing Wastes. I thought I was cured! but after two banters they all shut up again (Dorian, Bull, and Cole). How often are we supposed to be experiencing banter? Because that would make it easier to determine how wrong everything is going.
We've had reports from players without the Deluxe version running into it, good thought though.
I really wish I could give you a running average re: banter norm, but the folks who have dropped by our thread and mentioned that banter is quite common and happens quickly and such... well, they don't really have much reason to stick around, so I haven't been able to pick their brains for stats.
I think it might be prudent for a number of us to reach out to other threads and ask around. From the vid I watched (wish I could remember what it was) and the comments I've seen from people in other threads (including one in Story & Campaign in which players were all posting their favorite banter moments) the answer is "certainly more often than most of us are experiencing."
Based on their satisfaction as well as more than a few posts I've seen whereby people actually say they love that there's more banter here than in past games (!!) my current guess is... every few minutes, maybe?