Marsh is a lefty so he wouldn't break up the lefties. And as Murphy wrote today:
Harper didn’t get any benefit from batting in front of Schwarber.
In fact, he was his least productive self with Schwarber behind him in the order. The splits are pretty drastic. Harper’s OPS was nearly 100 points higher when batting in front of Bohm vs. Schwarber.
All small sample but protection really is a myth. Lefty-righty stuff can be useful esp with starters going so short and three batter rule. But gving your highest OPS hitters the most ABs is still the best thing you can do. And in the end, over a single season, the difference any of it makes isn't even going to be that big, or necessarily greater than the benefit of letting guys be comfortable and consistent, even if that's intangible.
They are pretty much just out of luck in terms of having a great RHB hitting fourth unless Bohm or Garcia can deliver. The question of whether it should be Schwarber-Turner-Harper vs. Turner-Schwarber-Harper is more interesting to me. We already now both of those things have worked pretty much the same in past seasons.