Wow. Am I the only one who think companions in DAI are more interesting than DAO and DA2, as well as their characterisation? Overall of course I mean, Blackwall, Iron Bull, Varric is a bit dull. I do think that DAO and DA2 have better companion interactions and connections to the PC, however, in terms of character, I find DAO companions more likable, while DAI companions, not all as likable, but more interesting.
I hated Sera and Vvn, thought Solas was just boring bald nerd, and Cassandra just a typical strong woman stereotype. But when I finally gave more patience and spent more time learning towards them, I actually enjoy myself hating Vvn, find Sera adorably annoying, respect Cassandra and her faith, and loves Solas character to death. And their character still give me surprises even in my second playthrough.
I like many of the companions and advisors. Some of the points you make are the reasons why I don't feel as close to them as the other games, DA2 especially. It's true, they are nuanced and more complex than some of the other characters from past games, but one of the difficulties is investing the time into discovering more about the companions. The banter issue is a big problem for this. But also, so much of the game is filler, read a journal entry, pick something up, quest completed, that it became more difficult for me to try and concentrate on delving in to the areas which DO have deeper content to them. The game is also so large that it would take forever to find all of the character details which only come out in specific locations or companion combinations, etc.
Cole, for example, provides a lot of insight into companions' subconscious, so if you never recruit him or have him in your party, you automatically miss out on a facet of the companion you have no other way of learning about. So yes, I think the companions are deeper, but it's more difficult for the player to discover the nuances of the characters and the gameplay does not help in this. One can blame lazy gamers who now expect information to be handed to them without asking, but the game should help develop characters without the player going through hoops to discover all of the content.
I spent my last playthrough trying to get Dorian and Iron Bull's romance to begin, but even after including them in my party for almost all of the maps, I didn't get close to having their romance initiate. A casual player would have no clue they could even pair up unless they came to these boards. We shouldn't have to work so hard to access character development.