Bill Cowher was D-coordinator of the Chiefs from '89-'91 (his only coordinator job). The Steelers won their division in his first year ('92) and were the no.1 seed in the AFC.
Frazier has been a coordinator for the Vikings for the past 3 seasons. The Vikings have finished 6th in total defense the past two seasons.
He was D-coordinator for the Bengals from 2003-04. He's worked under head coaches Andy Reid, Marvin Lewis, Tony Dungy (it was reported on ESPN a month ago that Chris Polian wanted Frazier to take over for Dungy instead of Jim Caldwell). He was even a first-ever HC for 9 years, albeit for a small school in Trinity College.