As a coordinator, the numbers aren't bad. Listed with team, year, job, and leading QB/WR/RB
1996: Steelers (OC) 11th: Tomzack/Charles Johnson/Bettis - Remember Charles Johnson?
1997: Steelers (OC) 7th: Stewart/Bettis/Thigpen
1998 Cowboys (HC): 9th: Aikman/Irvin/Smith
1999 Cowboys (HC): 11th Aikman/Ismail/Smith
2000 Dolphins (OC): 16th Fiedler/Lamar Smith/Gadsen
2001 Dolphins (OC): 8th Fiedler/Lamar Smith/Chambers
2008 Chiefs (OC): 26th Thigpen/Bowe/Johnson
A few things jump out:
a.) He's only had one bad season, but it was his most recent one.
b.) More importantly, how has he featured two different offenses with leaders named Thigpen?
c.) He's rarely had much in the way of talent. That QB list is awful unless you like concussed hall of famers.
d.) Most of this is old news. He's only really had one year coaching in the NFL since 2001.
So, I mean, there's no real conclusion here. He's not a terrible offensive coordinator: it's not like he hired Turk Schonert. He can manage an offense with medicore talent to above-average success. The real question is how does he lead a team.