I also want to voice my hope for additional content from Larian. I was sad to hear that Larian would not be doing more, mostly because they did a great job with what they did well! I came to this game in May, rather late, and a little later Larian announced there would not be additional substantial material. It left a small hope-shaped hole behind in my heart. I also have very much enjoyed this game, and admire the level of immersion it created. CRPGs will be treating the game's voice acting and expressive character personalities as a challenge to meet for years to come.
However, I do think that the bedrock of a CRPG is its story. This includes the narrative itself and the pacing. And when I hit Act 3, holy cow, did the pacing fall apart. The Act feels like it needs to be two acts, and splitting the upper and lower cities would probably have helped. Gortash and Orin need more context and discussion (especially Orin). The whole plot badly needs more structure. I think that when you kill the first of the two, time needs to advance a few days. Then you really should see panic break out in the city, see people stream out, and that all these last minute turf wars should die down. It really bothers me that Baldur's Gate is "business as usual" for most of the player's experience there. I can think of a few games that represented a city on the edge of a crisis (Majora's Mask, Dead Space 2) and in comparison, Larian really should have taken more care with the overall tone of the city--especially when the army is getting very close. (Come on, no horrible nightmares and insomnia with a giant netherbrain so close by?) There's really not a clear sense of progression through any narrative, as everything you do in the city is suspended in the same point in time.
I agree that the companions also need to be fleshed out more. I felt like I was railroaded into romancing Shadowheart, in part because the other companions barely have any scenes (except Astarion). More than half of my companions barely had a scene after after 1 and one obligatory quest in Act 3. And there's "that" companion, the Emperor, whose ending feels rather abrupt and forced. I think he deserves more scenes and a few more possible outcomes (spare his life in the battle, convince or force him to run, fight him in advance, etc). He's a great idea for a character, and his survival or not should be consequential, but the execution is really lacking. What you do with the guy should be a part of the decisions you make for (inflict on?) the world. But he gets kind of truncated as a character at the same time all the player's choices get funneled into three basic endings.
In any case, I understand that Larian has decided to make more ending scenes. I can only hope that this means they decide to stay involved. Act 3 needs substantial revision.
One more complaint: A modding kit that doesn't allow changes to text will not allow modders to fix these fundamental problems.