I think a forced fumble is worth more than a sack. Dumervil had 6 of them last season. That's pretty dam good. Sack totals go down when there's someone else on the team eating them up. The year he got 17, who else on the broncos had several sacks?
The fact teams account for him and QBs make mistakes because of him is hard to replace with a rookie or has been.
I'm confident a deal will get done.