You can save them, they will thank you at Skyhold, but most will be replaced even if they live. They are not important at all. I think my biggest gripe with DA:I in general is all about the details, i think the game is decent and i quite like it. Yet it is not a classic Bioware product. As i have said before i did not agree with The Witcher 3 open world design, but atleast they did pull it off because of the attention to detail.
I remember doing a quest in TW3 pretty early on, and when i got to Novigrad some npc ambushed me and i needed a moment to connect the dots, but it was an npc i wronged in that quest. It is just a minor thing ofc, but it is what seperates the two games alot.