I think Miami can win with Tua, but you're right they need more talent around him than with a Mahomes or Allen.Honestly I don't see any player on our team as being untouchable.
I like Waddle, and I believe this is Hill's last year. I think Phillips is a very solid and complete player (before injury). Holland, he is a safety, I wouldn't break the bank for that position.
Tua, I've never been believer, started to have a little hope last year, but he still needs everything to go well to really click. I don't ever see him a carrying a team, I think his play today is more of McD making it work (player design and personnel) , than Tua being anything beyond viable at the position.
The one thing to keep in mind about Tua, though, is he's probably never had even an average level offensive line. Without all the injuries last year, the unit was probably close to league average.
Fans were excited because the offensive line started to grow under Barry, which is a good sign. But it still needs work.