Out of *my* curiosity I just went back and checked the fic in question to see what exactly the dialogue was like. It was all short, sharp sentences with tiny, sparse narrative to make the switch (when there was any narrative at all between dialogue). I think that for it to work for me I would need longer dialogue (closer to a monologue than a short question/observation/answer exchange) OR I'd need more narrative in between, a couple of sentences at least.

But this only applies when the dialogue exchange is a loooong one and the padding between is consistently absent. I just know my strengths and I'm much better at narrative than dialogue, especially when I have to differentiate voices with no help from the author:)