That's where we disagree.
He is one of the key cogs that makes it all work in the secondary playing all over the place. I don't see anyone on the team who could replace him at all. If anything it would be a group effort and while you can get away with on a snap-by-snap basis this just reduces your variability and unpredictability.
I don't think DMac is particularly overpaid. He gets the same cash this year (9m) as Randall and Joyner. With Thomas, Mathieu, Amos and Byard making even more.
I stopped considering the prorated signing bonus when it comes to looking at salary / cap hits btw. because those are already paid out and solely an accounting construct.
There is only one player from the 4 who make more that I consider to be a better player than DMac. And quite frankly while Thomas is a better FS I am not sure he has the diverse skillset that enables him to switch competently between 4 different positions during one series.