Cherry picking with the blown save thing. The point is that the amount of injuries the Red Sox sustained directly affected their early-season performance. That is not debatable.
Innacurate statistic heavily influenced by umpire performance. It doesn't take a whole lot of statistical analysis to see that Red Sox pitchers fare worse with Salty than with other catchers. Not everything can be accurately measured statistically (yet) so don't waste your time with incomplete stats.
As for his offense, he's currently above average, but he's actually hitting over his head if you take career norms into account. It's not a big sample, but it's indicative of performance. Also, while his BABIP is not heavily inflated, his LD% is, and regression in that department is a big problem for low-contact guys like him, specially with an unsustainable 21% of his fly balls leaving the yard. Expect regression.