Spot on.I cringe when I hear more at bats in the number 2 spot. It might mean 18 more at bats over 162 games (once every 9 games). That being said, the number 2 spot has been filled by many stars over the years. What it can do is reduce rbi chances in the first inning. Unless Springer gets to second base, Vladdy is hitting without any one in scoring position. The number 3 hitter has a much better chance of an rbi situation...and of course the number 4 hitter can only bat if someone got on base in the first inning.
I estimated 10 ABs over a season as I imagine more last outs will be by guys lower down in the order or pinch hitters for an 8 or 9 hitter as opposed to your model of it being equally spread out.