implosion isn't a talent. its also not to be used in a single target situation at all. Also, most classes if not all, sacrifice single target for aoe unless its a talent (which implosion is not)
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that was the whole point of the talent. it was 33%(technically 33.33333~%) chance per shard, which basically amounts to 100% chance. it was a guarantee you'd get 4 imps.