It doesn't matter.
You don't have to be an awesome coordinator to be a great Head Coach. Can't you see that. It is a completely different job description. Philbin got the job because he made a great pitch about his vision for the Miami dolphins.
Look at Mike Tomlin and John Harbaugh. Those guys were no names before they became head coach.
I originally had misread what you wrote that you would want Rex as DC, and Philbin as OC. I would definitely agree on Rex, but disagreed on Philbin. My comment was really aimed towards Philbin, cause I wouldn't want him as an OC, or right now as a HC either. I agree with everything you just wrote though, you don't need to be a great coordinator to be a good HC. You do need to have a very high football IQ, which those coaches have.