I agree with all the others who say that a tragic ending for certain characters is appropriate and even expected sometimes. I also agree that the main problem with this game is that it was taken out of the oven far before it was fully cooked. (I haven't experienced any of the endings yet, since I'm still in Chapter 1. I've managed to stay mostly spoiler-free so far, but that doesn't mean I don't notice the grumblings of others.)
I feel that gamers in general have been brainwashed about this. There are very few other industries where we *expect* the product to be finished with either future work or worse, addons that we must purchase in order to experience the completed item. (This is why I do not like Mr. R.R. Martin's work, by the way.)
Also, I am not confident that Larian will address any of these things. I'm an ancient gamer compared to many of you, and I am completely jaded by what has happened in the past with other RPG games. Once the game is out, it may as well cease to exist for the studio unless there are serious game-breaking bugs.
And another thing to consider is that Larian may not have complete control over the characters' stories. This is a WotC game after all, and they are calling the shots. Maybe the story of Tav the female high elf barbarian and her companions is already set in stone like Abdel Adrian's story for comprehensive lore purposes, with all the novels and game manuals and other items that are probably being worked on right now.