The Miami Dolphins have been extremely proactive early in free agency. They were able to lure the top wide receiver and rejuvenate the linebacker position. They were also extremely close to signing tight end Jared Cook, but lost the bidding war to the St. Louis Rams.
Wide receiver was a pressing need for the Dolphins, and they were able to address it by re-signing Brian Hartline and bringing in Mike Wallace. The Dolphins should not be done addressing the position—there's still some talent in free agency and in the draft.
By addressing the linebacker position in free agency, Miami was able to bring in some younger bodies that can make an impact while letting go of some leaders with aging bodies. However, linebacker was not a position of need this year.
Miami will need to focus on adding an offensive tackle, a cornerback or two, a seam threat tight end, a pass-rusher and some more depth at wide receiver in the draft. Miami is not yet done in free agency so these needs may change, but as of now, these are the positions of need.