I think the "love at first sight" or "intense attraction at first sight" between E and D (along with the idea that their initial dislike only masked those romantic feelings) is a fanon idea, popular among JAFF readers and writers but I don't think it has textual evidence.
However, I also think that E and D are extremely well matched. They are both intelligent, moral (as in, want to do the right thing for rightness's sake), able to see their mistakes and learn from it, able to respect a person with different background and character than their own. They have strong feelings and aren't afraid to express them. Once they understand each other well, they become deeply attached. I definitely don't see them as a match of almost-convenience.
You exaggerate Darcy's faults, I think, and downplay their acquaintance. They did have quite a few conversations, e.g. at Netherfield, where he wasn't tongue-tied, and he learned quite a few things abouther character before he proposed - not to mention he learned I think the saw her integrity when she did not accept him for security's sake.
As for Elizabeth's faults, she wasn't as bad as her father in making fun of people (she didn't openly mock them and saw when they would likely be hurt and refrained from laughing then). Her judgment of Caroline Bingley was pretty much accurate. I do blame her for believing Wickham, but once she did so, I don't blame her doubly for also expessing her beliefs: she was championing the underdog, confronting a man above her own station, and throwing away security for the sake of loyalty to her sister and her friend, as she thought - in the first instance (Jane) she was right too.
