That is absolutely fair. I think we still don't know WHY certain endings happen and what the factors weigh in. It would be nice to at least retroactively look back at choices and go "aha, so that is why I got a bad companion ending".
I think this is important, too.
Spoiler from PoE ahead:
I say that to mean, at the end of the day, the best RPGs have you make your choices and live with them - that's the core of role-playing. In Pen and Paper rpgs that cRPGs are based on, the DM is not going to say "You have two choices, the good one where you'll get everything you want the way you and the bad one where you won't...which will you choose?", instead you're going to say what you do/say and the DM is going to interpret that as they see fit. I don't feel that anything PoE did was out of the pale with respect to that. Sometimes you're going to try to do good and it won't turn out well; sometimes you'll say the wrong thing and it won't be interpreted as you intended it. That helps make the situations and NPCs less like entities that only exist so the PC can 'win' and more like a responsive environment where choices matter in ways you might not expect.
We talk here about one single sentence, that turns the life of a person upside down, without any chance to explain myself or to correct it. In my opinion that is the opposite of lifelike. A conversation does just not work that way. You say something to a person. The person reacts. You clarify yourself, if necessary. A person does not lose her meaning in life in cause of a simple sentence(Maybe beside: "You are fired!" or something similar). It's normally a longer progress and involves many little steps toward a certain direction.
Its also no real choice if you interpret a sentence differently then the game designers. This kind of choice feels more like an accident. You take a dialogue option and get something completely different. Remembers me a lot about the Fallout 4 or Dragon Age 3 dialogues where you always had only a few words to choose from and very often did not get the expected answer. This happens less in PoE but it still happens sometimes.
In my opinion some kind of reputation-like system would be better. Example: A scale between "absolute good for sagani" and "absolute bad for sagani". If you do something that supports her view on the world she gets a +. If you do the opposite she gets a -. At the end we look at this scale and then we determine how sagani has been influenced by the watcher.