Suh's contract got restructured once to kick the cap hit down the line. And then he got dumped, even though it left the Dolphins with a big cap hit in future years - over $22 million the next two seasons. Von Miller's just got restructured so they could make moves. They also traded Talib away to save money. Do you really think either team would be anxious to sign such a contract again? If not, why on earth would you cite them as good examples for the Rams.
Yes, Donald will sign a huge contract. And the Rams will regret giving that much money to a defensive player. A fair contract would be tied into what a player actually contributes to winning, not based on what a few teams have given out and shortly regretted giving as major mistakes.
The Rams will benefit substantially in 2018 from bringing in AD - but it won't negatively affect their cap this year. It will start hurting them soon, and will be difficult to avoid if there is both a high average annual value and a high guaranteed amount. Fair would be a ridiculous amount guaranteed so he can compare to QBs, and an AAV that actually makes sense for a great defender in a league that favors the offense.