This is from an article by Andrew Healy.
I believe this may have been written before the McCain signing so it's relatively old. So maybe linebacker is the biggest need and cornerback is still a quiet need.
Biggest need: Cornerback -- Last season, depth was their primary problem, as Miami was the third-worst team in football at covering opponents' third, fourth and fifth receivers. And there is no guarantee that Brent Grimes will continue to be an adequate top corner, as he turns 32 years old this offseason.
Quiet need: Linebacker -- The Dolphins only have two linebackers on the roster with more than 10 career tackles. One of them (Koa Misi) has never started 16 games in a season.
Not a need: Offensive tackle -- Questions on the interior of line remain where left guard Dallas Thomas has struggled his first two years in the league, and prospective right guard Billy Turner barely played as a rookie but tackle looks to be set. LT Brandon Albert turns 31 this year and should still have a couple of strong years left. RT Ja'Wuan James played well as a rookie. Swing tackle Jason Fox provides reasonable depth.
I believe this may have been written before the McCain signing so it's relatively old. So maybe linebacker is the biggest need and cornerback is still a quiet need.