I think fans are always conditioned to be skeptical of their own guys. It feels like other teams have better staff, but the reality might be distorted. Oakland's numbers are good, but you do have to normalize for a VERY pitching friendly context ...
Tazawa leaves the ball up in the zone at times (especially oddly enough against Toronto) - which is dangerous in a high leverage situation - but overall has been quite good. Breslow, Koji have been good and honestly, Workman and Thornton for "other guys" in the bullpen are pretty good. What do you want out of your relievers late - pound the strike zone and get some swing and miss. Our top guys have done that (except for Breslow, though he has done it before, and his control has helped compensate some).