I'm definitely in the camp that see AJP's defense as below average, but do folks really think the effectiveness of a catcher is the primary reason why a pitcher does or does not have success? It's surely a factor, but I'd guesstimate that it's more in the 10-20% range.
I think it was fine for Fredi to play AJP a lot when he was white-hot offensively. Helps the team and sends a message to a young catcher who's reportedly had motivation / focus issues that the job has not been handed to him. Now that AJP has cooled down with the bat, he should absolutely return to a backup role.