I like Melancon, but 4 years and 60+ is not a worthwhile investment. I just can't imagine giving that kind of money to a guy who on the wrong side of 30 and has put up elite numbers with ho hum stuff. The uncertainty of ground balls turning into outs will always be an issue with the guy, and I think you absolutely need the high end strikeout artist at the back of the pen to give that kind of money to him.
Heck, Papeldouche had stellar numbers when he signed his deal with the Phillies and that turned out to be a disaster. There is a chance Melancon could be Mariano, but there is a better chance that he turns out to be Jeff Montgomery, or at least so says his BRef page. That same page also lists him with Joakim Soria, Greg Holland, Cody Allen, Kenley Jansen (those last two are funny honestly) and THE CHIEF CHAD CORDERO.