I think it's important to remember that Tua likely had more information on his injury than anyone else. If he had any reason to suspect he wouldn't be healthy close to the draft (or that his medical checks wouldn't pass), he simply wouldn't have declared. He could have easily run it back with Alabama, and would have been a top 2 pick next year even if he needed more time to recover. I'm sure Tua's doctors are confident he'll be healthy dinner than expected and that his physicals will all check out fine.
And Herbert simply isn't going to have the same grade as Tua going into the draft. Injuries aside, Tua was still considered a better prospect than Burrow (which is saying something). He won't fall past Miami, and anyone else who needs a QB will be asking Washington, Detroit, and New York (in that order) if they are willing to trade. Heck, Miami might be forced to pull something like the Bears in 2017, trading up themselves to ensure no one jumps them.
Miami would be a best case scenario trade down. We wouldn't lose out on the blue chippers, but probably get a second or a couple thirds for the trouble.