I'm having quite a lot of banter. About 5-6 between Varric and Cassandra alone, I think one with Varric and Solas, one with Solas and Blackwall... Not counting those in the prologue, cause they seem to be scripted.
It's quite random - sometimes you can go for 2 hours without hearing much, and then you'll hear 2-3 in one hour.
I think they've reduced the frequency a bit, because of several reasons:
1. The game is far larger, so if they did a lot of banter, they could start repeating themselves/stopped bantering all together midway through the game
2. There're no fixed banter points - In DA:O you could hear Alistair and Morrigan or Morrigan and Leliana banter every time you passed the little bridge in Lothering - in DA:I it's just random.
3. Frequency of bantering may be reduced if you're just exploring, compared to doing a major story quest - speculation on my part.