As the others have said in this thread, I think coaching has to be the #1 problem. While our talent level is definitely down from our successful days, I refuse to believe that we've struck out on so many highly-rated, nationally recruited kids. I think the more logical explanation is that the talent we've brought in hasn't developed.
I think the #2 problem has been QB play. Since Kenny D left, our best 3 QB seasons have been Berlin '04, Jacory '11 and Jacory '09? I think looking back, we definitely underappreciated Berlin when you compare him to the last few QBs we've had, but as a team that has run a pro-style offense, we've need either a good distributor or even a solid game manager at QB, and we haven't had that.
I think the #3 problem has been DT play. As a team that has run some variation of a base 4-3 defense for as long as I can remember, we've been at our best as a defense when we've had disruptive DTs. When our DTs blow up plays, it forces everything outside and lets our D use its speed, which has usually been the calling card of Miami defenses. Since big Vince left, we haven't seen great DT play, and I think our defense has suffered as a result