I agree with you. Cox has one excellent season and was merely average for the majority of the time he was with the Dolphins. Because of his hatred for the Jets and flipping off the fans in Buffalo, Dolphin fans loved him but he really was just an ordinary NFL LB when you examine his overall playing career with the Dolphins.
While he wasn’t a player, the most overrated hire in Dolphin history was Bill Parcells in 2008. He hired both Sparano and Ireland and then took the money and ran after a couple of years with the organization. With Ireland left to select the talent once he departed, the Dolphins became one of the bottom tier team in the NFL and only now are they hopefully headed in the right direction.