Edit: Though the infamous "I will protect you" line probably annoys me more than even the companion dialogue at the dock.
Its been a while, can you please add some context? I dont remember the line! Thank you C:
Oh, I am sorry. I was talking about the "I promise I'll keep you save always. You'll never need the power of an Ascendant." line that shows up after abandoning the ritual.
I despise this line. First of all it is insincere, especially if you play as a human or another race with a short lifespan, but even for an elf their eternity is relatively short compared to that of a never aging vampire. It is also insincere in and of itself and exactly the trite sweet nonsense that was made fun of during Act 1.
Secondly it renders the whole non-ascension path moot. The non-ascension paths for both Astarion and Gale is about them being enough as they are and that power is found in trust and friendship/love, in balancing each other out rather than in making the ultimate power grab in the vain hope of compensating one's insecurities. They are both enough just the way they are.
A line about how Astarion helped the player character in the past, or an affirmation of the two of them having each other's back would have been much better here. Astarion has several lines to that effect, the player has very few. I think the "no matter what happens, I got you" that leads up the graveyard is the only one.
Regarding Karlach. I'd rather not have her dialogue there changed because this lashing out is part of her. She has a couple of moments during which she makes another person's problem only about herself, for example when Wyll is charged with Mizora's quest in Act 2. In this instance you can call her out for it and I found that rewarding. The self-centredness that lies beneath her whole cute and peppy demeanour is one of the few things that make her interesting as a character. Otherwise she is just a cute Mary Sue everyone is supposed to love.
I think there are also versions of the dock scene with Astarion's Origin on yt. You have to ignore that he's in underwear, but it has most of the companion comments.