With the catchers, I agree with earlier posts that Mauer deserves to be in Tier 1. That's as much a testament to his ability as it is the fact that V-Mart isn't exactly a consistent hitter that doesn't go through cold spells (unlike Pujols at 1B, A-Rod at 3B, etc).
Tier 4 seems a little high for Jojima. He flashed great power in Japan, but we know that isn't a lock to translate to the ML, especially playing in Seattle. The Pierzynski-Barrett tier would be a better fit for him at this point.
I would eliminate Closser and replace him with Yorvit Torrealba, whom the Rockies acquired and intend to give every shot to be the starter.
If you're listing guys like Matheny and Zaun, I would just go ahead and put Damian Miller, Dioner Navarro, Mike Lieberthal (who could conceivably be a little higher), Jason LaRue, John Buck, Toby Hall, and Brian Schneider. I also like rookies Jeff Mathis and Josh Willingham, as they look to be option #1 for their teams at this point.
I think the first three tiers of OFs are on point.
I would sneak Beltran into Tier 3. He was awful this season, but he's going to have a MUCH improved lineup and a lot less pressure to excel.
Vernon Wells had an off-year, but he's a Tier 4 guy in my eyes.
I don't know if Dusty is going to give Pierre a green light; I would flip-flop him and Wells.
Most of tiers 5 and 6 seem to be complete personal preference; for instance, I'm higher on Hunter and Drew and cooler on Dye. But it's your list, so whatever five and six look like is just a reflection of your thoughts.
Chone Figgins qualifies in the OF too, as does Ryan Freel.
Players that I think are at least as good as the ones you have in the bottom tier: Jeff Francouer, David Dellucci, David DeJesus, Raul Ibanez, Reggie Sanders, Aaron Rowand, Curtis Granderson, Brian Anderson.