Dovetail this signing with the thread about PFFs ratings of the position groups available for the draft.
They ranked the IDL position as the single weakest group in the draft, called the DTs the weakest group they have ever ranked since their inception.
Given that, signing a journeyman, run-stopping Tackle makes more sense.
Also, in year 1, a journeyman runstopper is likely to be a better runstopper than a 1st or 2nd RD rookie will be. Miami has a strong rotation of guys who are huge and can plug things up.