Bucksfan's assertion is that there isn't really much of a correlation between scoring a lot of runs in a given game and having a good offense overall.
I contend that there is. Here's some data.
What does this mean?
Firstly, we can see a pretty clear general trend from the top left to the bottom right. The left to right part is definitional -- every team scores at least 0 runs 100% and scores at least the next amount of runs a bit less frequently.
Within any given level of run scoring, teams that score the most runs on average are most likely to score that level of runs or higher.
For example, looking at 10+ runs, the Brewers, Cards and Rockies (top 3 average R/G) did it 6%, 10% and 8% of the time respectively. The bottom 3 teams in overall run scoring scored 10+ runs 4%, 2% and 2% of the time. Put differently, scoring about 1 more run per game correlates to scoring 10 or more runs 3x as often.
And as you can see from the correlations, it's generally all quite strongly correlated. There are points at which the randomness takes over, but that's only at the very extremes -- shutouts (really bad day) and crazy explosions of 14 or more runs (really, really good days). The way to read that is, the more the number, the more that teams that do the thing in the row (e.g. score 5+ runs) are the same teams that do the thing in the column (score 15+ runs).
In conclusion: At least in 2012, there did not appear to be any team where the average number of runs per game hid the fact that they were particularly prone to extreme run outputs -- high or low. Put differently, teams that score more runs on average tend to have their entire run scoring distribution shifted higher, particularly in the 3 to 8 run range.