The Diablo III Forums now offer the outcome of the second "Ask the Devs" session discussing in-game with the folks behind Blizzard's action/RPG sequel. Many of the questions about bugs and other long-standing oddities were posed, but enough of the answers remain vague that there is another thread suggesting they not even bother with these in the future, though several posts from Blizzard point out they've been asked to be more transparent about plans, even when they are not yet concrete. The outcome certainly can be confusing, as shown in these two sentences pulled from the same answer from game designer Travis Day:

Best-in-slot is a subjective term. What is the best for one class or play style isn't necessarily the best for everyone.
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The problem today is that we have items that are universally best-in-slot, regardless of your class or build. Right now, items that are best-in-slot for a Demon Hunter are probably also best-in-slot for a Monk, and that's one of the big things we're looking to address.