It's not necessarily foot dragging. Miami is a private institution. That makes it much more difficult to get access to information during the course of an investigation, even if they are just trying to verify the work the Charles Robinson has already done.
Also, I don't see the precedents set in the PSU cas as being applicable here. First of all, as somebody already mentioned, PSU essentially self-reported everything. It was a higher profile self-report than most others, but that's what the Freeh Report was. Secondly, the NCAA interpreted the situation at Penn State as being mainly violations of the NCAA's constitution, rather than specific bylaws. I'm not sure that they even had a process established for dealing with such a thing up to this point, where on the other hand they already have a well-established (if not slow and cumbersome) process for dealing with alleged bylaw violations.
There is also the possibility the Penn State had their due process cut off by the NCAA. I think the NCAA took a calculated risk that Penn State wasn't going to dare challenge anything on those grounds because keeping this scandal in the news is disastrous PR for the entire university. If the NCAA cut corners with due process in the Miami investigation though, I think they'd have a fight on their hands that could torpedo the whole thing.
They should take their time, be thorough, and get it right.