To me, the full "defensive value" of a catcher is very hard to quantify, especially things like "getting the most out of the staff" or CERA type data, framing pitches, blocking passed balls and WP's and more.
Time and time again, Vaz has under performed with pitchers when compared to our other catcher.
I like Vaz, but I don't see him as an overall plus on D, when everything not having to do with offense is factored in.