1. - agreed.
2. - Generally agree that invisibility shouldn't work as easily on everyone, BUT - it should be skill level related, so whether any specific enemy would manage to detect you or see you should depend on the skill check between your skill in that magic and his own. So characters who invest more get to actually feel it in the game.
3. - Trait dialogues are fine as they are. When they work as they do now, it all gets a bit of a wacky fun effect, (Larian game right?) - and plays like a small randomizing element addition to the gameplay.
I just like to roll with it, and never really try to game it.
It keeps things fresh, as some traits change over time and i have to adjust for that. Or i suddenly notice Roderick is immune to crippled just right in time.
Or some other character gets better at something else.
It really isnt a feature that needs to be min-maxed.
+ Different results that seem "weird" to some players should be looked at as just a bit of Larian type of making a bit of tongue in cheek fun of it.
4. - agreed, yes.