I agree that we are not attempting to "slam" anyone's work. Not mine, yours, Maier's, or anyone elses. That much we can agree on.
However, I am still confused about this holistic rubric that we are supposed to be applying to Vivian Maier or HCB (or Weston, Adams, et al.) I will be the first to admit that I am not an expert on what "art" really is but I do know that there are those out there who consider Steve Ditko's work on Spyderman to be great "art." What standard of performance has been used in that case is probably up for discussion as well. But, if you consider art to be, the expression or application of human creative skill and imagination, typically in a visual form such as painting or sculpture, then in my opinion, Vivian Maier's work certainly qualifies IMHO.
Now, where she stands in relation to other photographic artists is a completely different question, but that seems to be where this thread has been going. It has been stated that she is not in the same category as Henri Bresson, and because of that she does not qualify as "great." That, IMHO, moves our discussion away from any "artistic rubric" and turns it into a popularity contest instead. I do believe that much of her work was considerably above the norm, so I consider her to be a great artist. Now, is she as great, or greater, than some of the other artists whose names have been mentioned? I do not know.
To go any further I guess we need to know what standard of performance needs to be met to reach greatness?