They can kind of do that (designated runner thing) if they are of a mind. Naquin can replace him the first time he reaches (or Ruf, if they expect a lefthanded reliever going forward). That way, still have a guy who can hit in there who is a capable runner, but they get the advantage of the stongest hitter up until then. Gore can be used later if they need to pinch-run for Alonso or the catcher, or even take over for Ruf or Naquin. If both Vogelbach and his Ruf/Naquin replacement have reached during the game, leading to a Gore getting a plate appearance in the DH slot, well, they've probably had a pretty good game. If the game is still in doubt and you don't want Gorgasm at the plate, the Ruf/Naquin figure that hasn't been used is still available. DH managing makes it less risky to spend some of your bullets early.