A big problem for me is that the companions don't really interact with each other (outside banter which is bugged for many people). There are some personal quests which involve another companion like Cole's and Cassandra's but for the most part they stay in their own areas minding their own business. Companions interacting with each other (and with quests) was one of the things DA2 did well. In DA:I they also don't really interact with quests like they did in DA2 and sometimes in DA:O (example Fenris squeezing people's hearts to get information, Varric spinning lies about things like you being a first enchanter or Feynriel being the viscount's illegitimate son). I miss those touches.
I have to agree with the above post. The banter bug, which has been a problem of varying degrees for diff ppl, really opened my eyes. It opened my eyes to the importance of party banter. I thought party banter was just a nice perk and something I really enjoyed. Now, however, I realize how important this field banter--between party members; comments on the areas you're in; and comments/insight in regards to the quests you're on.
The party banter really helps to build a sense of kinship with these characters, and witness a growing bond between the characters themselves.
Mind you, I loved all the dialogue options they had in this game. Loved it! The dialogues were in depth and not confined to a small cutscene only thing. You could get backstory and everything in DAI. It was nice. I hope BW keeps up with this dialogue options depth and interactivity. (I also loved the romance dialogues. lol! I thought they were well said and far more subtle flirtations than in previous games...)
Garrus, et al, did have 3 games, though. There were many battles fought together. Much history together. So, yeah. You're gonna feel closer to them after all that. I love the characters in DAI, but there is something missing...i'm not sure what...maybe a sense of Team? idk.
Don't misunderstand, though. I very much enjoyed DAI! Criticism of a few things here and there does not negate that. But I understand where the OP is coming from. Sometimes I think that having the companion base as a smaller campsite setting actually contributes to a sense of team. Everyone kinda stuck together, toughing it out and roughing it together. Simple proximity sometimes makes a huge difference in terms of a sense of bonding.