Started a new game, made sure that when I was prompted to venture forth to the Hinterlands at the war table in Haven that I accepted, and have been religiously clearing off all new items / quests / codex entries, plus travelling via map exit points / war table only.
Have had more banter in the first few hours than I had in my first playthrough total. It's amazing.
Occasionally everybody does go quite for a stretch of time after the first 3 banters, but then they all start up again. In fact I even had 4 banters between Solas and Vivienne in the space of 5 minutes.
So add me to the list of people who seem to be having success with these methods, hopefully that aids with the debugging.
To all the angry people, Bioware *need* to be able to reliably reproduce this in order to fix it. It's not enough to watch videos or listen to the pages of complaints. If they can't figure out the exact set of variables that trigger the problem, then they have zero way of knowing if any fix they implement actually works. Can you imagine how much angrier people will be if Bioware make some random changes, advertise it as being fixed, but then it's still broken for everyone?