If they add a catcher before it is closer to the trade deadline it will just be another .200 hitter with better defense. It is the least of their problems compared to 3B and CF (and even the bench, depending on how those two things shake out).
I think the season has probably exceeded internal expectations, even if phans don't want to hear it. They knew they'd probably only get to July with 4 good starting pitcher options, they just didn't know which two would emerge. They knew they would have to use six or seven starters (as always). They certainly didn't know the bullpen would be decimated or that we'd lose 2/3 of the starting OF, and yet, still a playoff team with only 10 games to the midpoint.