While there are some actions that I can predict will result in some characters being upset or happy (i.e. Wyll if you choose to side with the goblins against the Tieflings), I'm often surprised when I select a dialog choice and somehow that results in 3/4 of my companions disapproving. Prior knowledge of how my companions will react to some of my choices really would influence my choice or at least make the choice more compelling. For example if I'm really trying to buddy up to Gale, I'd like to at least be able to guess at when I'm approaching a moment where my decision might impact our relationship. The problem is that there aren't any contextual clues that provide hints that what I'm about to do will have important consequences - instead it feels kind of like tip-toeing through a minefield and any wrong step can arbitrarily result in "Gale Disapproves" without any intention on my part.

I can think of a few solutions, but what I don't want to see is an obvious "this will make Gale dislike you" warning. I don't want my hand held THAT much. Give me just enough information to make relationship management something like a minigame and reward players for paying attention.

Then again, maybe I haven't paid attention enough and those clues are already there?

Like a lot of RPGs with affection systems, I imagine we're supposed to learn the preferences by trial and error. As arbitrary as it may seem, there are some consistent patterns to what party members approve of, though some obviously clash with each other. Gale likes Diplomacy and Conflict Resolution, Lae-zel likes forcefulness and agression, Astarion likes showmanship and confidence, and Shadowheart likes manipulative and aloof behavior. Some of that is readable from their personality and the things you learn about them in conversation.

Thank the gods I can exactly predict how this person I basicallly just met will react to everything.

No, we shouldn't be able to do that.
We should learn about them from their conversations and their reactions to our decisions.
But there should be more reactions from them after we do something they like or dislike to show their character a little more.
More discussion of major and minor decisions back when we're at camp, so they can tell us their opinion on things.

From what I've seen you just don't know the characters well enough yet, if you think their reactions are arbitrary.

The characters seem to make sense when you understand their background and motivations. Characters wont just have a different opinion on what to do in a situation, they will have a different interpretation of what the situation even is.