I was sort of curious if that was true, and I was actually surprised to learn that it's not.Even with the offensive losses, we will be better on O next season.
However:
1) We need to be twice as good to even be average
If we look at yards per game, if the offense doubled it would be 3rd best in FBS. By points per game, doubling would be 11th best in FBS. Although that was just a quick sort at espn.com, and I don't know if those points include defense points.
I looked at the stats section of ncaa.com, and looked at the various offensive stats, and it's pretty universal almost no matter the stat: we were always in the bottom 10, and often bottom 2-3.
But, if we doubled our production, we'd be consistently in the top 10, and often top 3.
OTOH, if we improved by a more modest 50% or so, that would make the offense pretty average.