With the exception of the “Cars” franchise, Pixar themselves are the exceptions to the usual law of diminishing returns which normally plagues sequels. However, in landing a sequel to “Finding Nemo”, a perfect story which really needed no follow-up would Pixar flounder or would the carping prove bass-less? A year after Nemo safely returned to the reef, Dory (Ellen DeGeneres) has a sudden epiphany…