Re: stealth mode, I wouldn't use it otherwise, but it is the only way to detect secret treasures. That sucks. There should be a passive detection aura around the characters that is just better while actively searching.
Re: NPCs, I agree that they are much less interesting than in Torment. Most still have something of a personality, though their personal quests seem quite lackluster. For example, the endings to Kana's and the fighter types quests are completely unsatisfactory. The way you talk about them with the characters changes nothing about them, whereas in other games you can actually have an effect on your companions. So yeah, that is...less than it could have been, really.
In general, I'm starting to feel the game is a giant fan service. They are rehearsing Baldur's Gates without putting in anything new other than somewhat different game mechanics. The writing feels a bit lackluster considering the time and money they had to put into it. The way they did those backer NPCs is just stupid; there is no reason whatsoever to read their stories. Had it been so hard to include them in the side quests? The stronghold is likewise a bit glued on, since it doesn't attach to any missions.
For example,
there is that young elven girl who has been raped by her uncle. Why can't we choose to offer her a place in our stronghold as one way to protect her? It is what my kindhearted traveler paladin had logically done.
So yeah, the game is a sum of several parts that don't really fit together properly, while at the time being overshadowed by the masterworks it seeks to emulate.
Don't get me wrong, I still like the game, but... it is mainly because there haven't been any good party-based RPGs for a loooong time. When you are starving, even bland bread seems like a feast.