This is what happens sometimes when you get to play a 4th place schdule in a division that, after Brady got hurt, was nothing special.
They snuck up on some people last year. That won't happen this year. AND they're playing a more difficult schedule
So, unless you believe that the Dolphins are truly "for real", you can expect to see a regression back toward the mean. I have not specifically looked at their schedule but 7-9 to 9-7 seems about right.