Quark: Quark is a good character that was often poorly used, especially in the later seasons. When interacting with the rest of the crew, his banter and unique perspective could be the highlight of an episode. But as the series developed and the cast fragmented into their own groups, Quark was often left interacting with other Ferengi in lame comedy episodes. when Quark is on form then he's one of the best things about the show, and when he's off form he's one of the worst.
I agree with all of your assessments except this one, mainly because I'm less harsh on Ferengi comedies than you are. But I also think, even in bad episodes like, say, "Profit and Lace," Quark himself isn't a bad character. But I guess that's a subjective thing. And I definitely agree that he could've been taken in better directions.
I could go on and detail my opinions on the recurring characters, but this series review has been delayed enough.
Umm, now that the series review is done... could you go back and do this? Your analyses are extremely well-done, and I'd love to see your views on, hmm, all of them. (But especially Garak, Dukat, Damar, Weyoun, Winn, Bareil, Ross, Nog, Rom… um, yeah, all of them.) Pretty please?