Miami's main problem this year is not that they don't have a #1 WR, it is that they don't have a legitimate 3rd WR to throw to. The Dolphins don't need another Brandon Marshall to target all the time. They have tried that and it doesn't work. Miami just needs a 3rd reliable option. Nannee and Armstrong have both been an epic failure!
Your theory on targeting Marshall so much sounds great, if it were only true. When did Miami start winning games last year? When they stopped targeting Marshall so much. Miami was 1-6 last year when targeting Marshall 9 times or more and 5-4 when targeting him less than 9 times.
Under the Ireland/Sparano regime lasting 4 seasons (2008-2011):
Miami's Overall Record: 31-33 (plus 0-1 in playoffs)
Miami's record without Brandon Marshall: 19-15 (.559 winning percentage)
Miami's record with Brandon Marshall: 12-18 (.400 winning percentage)
Miami's PPG (Points Per Game) Offense 2008-2011 (64 games): 20.4
Miam's PPG without Brandon Marshall in 34 games: 22.0
Miami's PPG with Brandon Marshall in 30 games: 18.6