Well like the OP said none of the young players have stepped up to compensate, though I'm not sure I ever expected Bohm, Marsh or Stott to be able to do so. This team just never replaced Hoskins in the middle of the order, and now Harper's out (and aging himself). Imagine if Schwarbs was still leading off (though it seems that hasn't gotten him many more opportunities with men on base).
I don't think the team is playing above its head though. It is built around starting pitching. Just not sure that does it in October.