Odo & Garak: agreed. They had a genuine raport, and again, shared outsider status not just at place of residence but in regards to their respective people. But other than the two parter which started to point this out, I recall only one other episode or so which had a follow-up scene. And then nothing. Which wasn't enough to call it a friendship.

Quark & Rom: I adore that relationship, but I do see family relationships in another category, and the way Quark and Rom relate to each other, both the negative and the positive, is too interlinked with them being brothers to see it as a friendship that just happens to be between blood relations. I mean, if Rom was a Ferengi waiter unrelated to Quark, most of their interactions would have happened another way. (And we have a point of comparison via Pel, because Quark didn't know she was a woman for the majority of the episode - to him, she was a waiter whom he happened to like.)