The Dolphins are in good shape with regard to the percentage of the salary cap allocated to Tannehill, as they have a starting quarterback who functions on average somewhere between the 50th and 80th percentile in the league, depending on your view of him, and who has a corresponding salary cap hit.
Where they have a problem in my opinion is in allocating so much of a percentage of the salary cap to Suh, who is certainly one of the top players at his position, but who doesn't have enough of an impact on opposing passing games to warrant it.
The situation they're facing with Tannehill and Suh, combined, is that they have a quarterback who performs at a level such that one of the league's best pass defenses is needed to contend for a Super Bowl, while a player who does nowhere near what's needed for the pass defense (Suh) is busy absorbing a great deal of the salary cap money necessary to assemble and pay such a defense.
That's a rather "stuck" position. You need either 1) a better quarterback, in which case you can contend for a Super Bowl with a worse pass defense, or 2) Suh's money freed up, so that the necessary pass defense can be assembled and paid.
If I were running the team I'd approach Suh and indicate all of this to him, ask him how badly he wants to win a Super Bowl with the Dolphins, and then either trade or restructure him, based on his response.
Tom Brady takes regular pay cuts to help keep the Patriots highly competitive. It's time to consider asking Suh to do the same in my opinion.