The idiom "dreamed a dream" is clearly an example of the cognate accusative, known from Hebrew and other ancient languages, in which the verb is followed by a noun (here used as direct object or accusative) deriving from the same root. From this, it also seems likely that the words "seen a vision" represent another cognate accusative. We can illustrate this by rendering the English as "seen a scene," "vised a vision," or "envisioned a vision." It is likely that the original read , using a verb and noun deriving from the same root as , "visionary." The fact that this Hebrew root is found in cognate constructions in both Isaiah 1:1 and Ezekiel 12:27; 13:7, 16 adds strength to this suggestion.Just one of many examples of Hebraic influence in the Book of Mormon.
Update: This example is actually not one of the more interesting ones because the term "dreamed a dream" is also present in Genesis, as BYU Alter Ego points out in a helpful comment. But there are much more interesting Hebraisms that cannot be "explained" by their presence in the Bible. More interesting in the present case is the "visionary man" concept that Tvedtnes discusses in the original article.