Unless you were lucky enough to get your "optimal" or "desired" build, meaning you have the right amount of Intellect, Discipline, and Strength for your character then you have no reason to waste your shards yet seeing as there is no reason be 32.
[spoiler]32's are dumb...[/spoiler]
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I want 32 so i can solo crota.. Also, anyone waiting for multiple raid pieces just to get a specific roll has a serious problem.