It doesn't really matter if Salmons is a good defender or not, he has a reputation of being a good defender (come on, surely we've been over this ground in the BG threads about how often it's mentioned about Salmons improving our defense to compensate for BG). I mean you're using Noc's reputation as a good defender when he's not to justify him getting a contract, I think the same goes for Salmons.
The MLE will go down a bit with the cap, so a 3 year MLE deal is about 3/18. If a team gets Salmons for significantly less than that I'd be shocked. If he could have opted out after scoring 18PPG then he'd have gotten more. There's not a 18PPG scorer in the league who got a contract for 6 million a year (outside of the guys on rookie contracts).
I also think you vastly overrate what you can get for the MLE. The majority of MLE signings end up being deals the team signing them regrets. There was an article I can't find right now that analysed production vs salary of non-rookie contracts and found there was a huge dip right at the MLE level. The MLE typically goes to guys who aren't worth it but get bid up to that level because any team can pay it.
I mean Jerome James, Radmanovic, Olawakandi, Jeffries, Cardinal, Udrih, Tim Thomas, Kapono, etc etc etc. There's always some dumb team that will pay. It doesn't matter what Salmons is worth, it's the NBA, he'll get paid.