Unit selection should work like it did in BG1 and BG2. The whole idea of chaining portraits is novel but in practice is just very inconvenient. Constantly people follow you into hazards, break stealth, etc. Simply add a speak button for talking to NPCs and let us click and click drag to select multiples.
I completely disagree, I love having my characters grouped with chained portraits. Yes it breaks stealth sometimes, but that is just where you need to be onto it aha... much better than the click and drag to select units like you speak of IMHO.
Just a thought.. but both ideas are pretty terrible. I think stealthing and traversal up and down terrain is where I've noticed these issues the most. I think a simple setting allowing players to toggle a choice in how they behave when encountering these situations is best.
I'd personally prefer to have all chained characters stealth if one person does. This way if I want ONE person to sneak or ONE person to not sneak I can easily control it, and quickly.
The terrain thing is a bit of a different beast and i just think the AI needs work in that regards. There should also be a little button next to the portraits that breaks all the chains at once.
Since we can already hot key portrait selections I see zero reason for the click drag click functionality to be implemented other than enabling for easier accessibility to the disabled gaming community.