D3 ball varies greatly across the country. A few years ago I sat and watched a Beloit College vs St Norbert game and both starting pitchers were throwing in the mid to high 70's... St Norbert had a 3B who really stood out (forgot his name, doesn't matter) with great bat speed compared to the rest of the field that day. Later in talking to one of the St Norbert coaches he said that the kid had numerous mid major D1 offers but preferred to stay closer to home where he knew he would start and bat 3rd in the lineup from the first game of freshman year through his entire career...
the D3 teams that go to the college World Series would whup a heckuva lot of D1 teams. The worst D3's in the nation would get destroyed by the best high school teams in Illinois, let alone Texas or Florida. It really varies
If my son ends up going D3, I would look at the potential of him being drafted as a lottery ticket. There would be a multitude of other considerations that would come into play as to choosing the right fit