I would argue, in that specific case, that the cumulative build through the series is more important than in many series.
I really am reluctant to give this series any more of my time. But, in order to go the extra kilometer to ensure that I am giving it a fair chance, I purchased "A Betrayal in Winter" today. I have quite a lot of books waiting to be read, but I will try to read it when I can, and reevaluate my impressions if necessary.
Though I would also disagree with you on the quality of the characterisation, so some of this may well be down to taste.
Could be. It is my belief that there are a number of factors that people use, sometimes consciously and sometimes not, in order to arrive at their final estimations of "good", "bad", "excellent", "a failure", etc. I believe that without quite a bit of context and insight into each person's thought processes, those evaluations are nearly (or even completely) worthless. I have seen seemingly intelligent people who prefer brevity in terms of characterization and seemingly intelligent people who prefer that characterization be written in as much depth as possible. The fantasy author Robin Hobb is a good example of the latter preference, someone whose writing very much appeals to a portion of the audience, though at the same time there are readers who are very much put off by her style, sometimes with a passion. I don't know if you are familiar with her work, but it struck me as a good example to contrast with Abraham's.