With Darcy it is hard to build a case either way. We are told his obvious, displayed faults. We are told he is "amiable in other company" - presumably those he feels comfortable with - wen can only guess as to how large that group is. Perhaps the key information we are given - and info that may be more relevant to JA's tiume than ours, is the testimony of Mrs. Reynolds and Elizabeth's assessment of the condition of his house and estate. I always have been left with the impression that Elizabeth's acceptance of his offer of marriage is based more on respect abd prudence than passionate love. But that's just me.
In regards of Elizabeth, i think we have to make allowance for her age and lack of exposure to a broad range of society. I doubt she ever had occasion to meet a glib seducerr/con man such as Wickham. He was outside of her experience. Her immaturity shows forth in her dissing of Darcy. I do wonder if she would have been quite so credulous with Wickham if her vanity had not been so badly tweaked by Darcy. She may very well have been.