I made up these metrics...but they make sense to me.
Let's say scoring 4 runs a game is mlb average. I think that is close. In all our 88 games this year we avg 4.7 and opps avg 4.3. Based on a 4-run avg, I divided up our losses between "blame it on the offense" (we lost even when the opp scored at or below avg - 4 runs or less) and "blame it on the pitching" (we lost even when our offense scored more than average, meaning 5 or more).
Blame it on the offense -- 18 losses
Blame it on pitching -- 8 losses
Blame it on neither (we just lost) -- 18 losses
Based on this simple analysis the offense has cost us 10 more games than the pitching.