Obviously the head coach gets the wins and losses but as a general idea of how their teams did with them as OC's ....... admittedly there are much better criteria for OC, so your point is well taken !
If you use total offense as a criteria to evaluate OC's ....... in 4 years, Gattis teams have averaged a ranking of #64 (skewed by one great year at Michigan) and Cignetti teams in 12 years have averaged #66 (skewed by 2 great years at Fresno State) ........ in the last 3 years (since Cignetti came back to the college game), Gattis (at Michigan and Miami) teams averaged #63 and Cignetti (at BC and Pitt) #75 ...... Gattis in 3 years at Michigan averaged #57 in total offense and Cignetti in 3 years at Pitt has averaged #58 ........
In scoring offense, in 4 years Gattis teams average ranking is #56 and in 12 years Cignetti #53 ..... in the last 3 years, Gattis teams averaged #60 in scoring offense and Cignetti #68 ...... if you take out the Fresno State years from Cignetti's record (posters say that skews his record), then in his last 8 years that he has been an OC (without Fresno State) Cignetti's teams have averaged #60 in scoring offense.
I would say that even though he has coached at lower rated football schools, Cignetti's record stacks up very well compared to Gattis and I think highly of Gattis.