Speed is fairly useless if you don't have the instincts or playmaking ability to take advantage of it... It serves no purpose if it's only preventing you from making mistakes, as opposed to FORCING the other team to make mistakes...
Most of the best safeties that have ever played this game weren't fast at all. You can attack just about any safety that's ever played this game matched up vertically with a blazing speedster 1-on-1 and make him look silly... but that's where film study and instincts allow you to overcome that...
Steve Atwater made 8 pro-bowls and should be in the Hall of Fame... he was a 4.6 guy..
John Lynch made 9 pro-bowls, he was a 4.64 guy...
Hell, Rodney Harrison was a 4.8 guy...
I doubt many of you are old enough to remember Kenny Easley... he was a mid 4.5 guy...
Leroy Butler, Darren Sharper, Darren Woodson, Ed Reed, Eugene Robinson, Carnell Lake, Donovan Darius, Carnell Lake, etc... all these guys made a living off of instincts...
I've seen Chris Clemons take plenty of bad angles and give up more big plays than he should, I don't care how fast he is. He's a nice little player, and was a much needed upgrade over Gibril Wilson... but Miami needs a playmaker at the safety position...
You don't really want Reshad Jones in a position where he has to transition and turn and run with speedy receivers down the field... Hell, you don't want Ed Reed turning and running with wide receivers in man coverage either....
However, Reshad Jones is capable of making plenty of plays on the ball in the air in zone coverage, the same way a lot of the best safeties that have ever played this game have...