CERA's value is when comparing only catchers on the same team AND pitcher by pitcher with significant sample sizes. I'm not sure the sample sizes are large enough to compare, plus Vaz wasn't playing last year and Swihart wasn't really playing this year. Comparing how Vaz did with Porcello this year vs how Swihart did with Porcello last year might not be fair. It's hard to fully blame the catcher for Porcello's Jekyll and Hyde show.
The sample sizes are all whacked out, but here they are:
Porcello:
2016: Leon 2.52 (107 innings), Han 3.45 (16), Vaz 3.64 (94), Swi 6.00 (6)
2015: Han 4.15 (39), Swi 4.47 (107), Leon 7.86 (26)
Career: Leon 3.57 (134), Vaz 3.64 (94), Han 3.95 (55), Swi 4.55 (113)
Price:
2016: Leon 3.23 (109), Hola 4.15 (13), Vaz 4.62 (97), Swi 5.73 (11)
Buchholz:
Career: Hola 2.25 (8), Leon 3.01 (155), Vaz 4.44 (130), Han 5.93 (27), Swi 10.00 (9)
ERod:
Career: Han 3.78 (50), Swi 4.08 (71), Vaz 4.50 (22), Leon 4.60 (86)
Wright:
Career: Swi 1.35 (7), Vaz 2.72 (36), Han 2.90 (90), Leon 6.46 (24)
Pom:
2016: Hola 3.32 (41), Leon 5.85 (20), Han 7.88 (8)
Barnes:
Career: Hola 0.00 (3), Vaz 2.02 (27), Swi 4.50 (30), Han 5.93 (27), Leon 6.14 (29)
Ross:
Career: Hola 0.00 (3), Leon 2.28 (47), Han 2.84 (32), Swi 4.94 (27), Vaz 12.86 (7)
Hembree:
Career: Swi 1.20 (15), Han 1.83 (20), Hola 3.00 (3), Vaz 3.08 (26), Leon 5.48 (21)
Uehara:
Career: Han 1.12 (24), Swi 2.60 (17), Leon 2.86 (28), Vaz 5.35 (35)
Tazawa:
Career: Vaz 3.06 (35), Leon 3.16 (26), Swi 3.86 (28), Han 4.10 (37)
Kimbrel:
2016: Han 1.74 (10), Vaz 2.04 (18), Leon 3.20 (20)
Kelly:
Career: Vaz 3.06 (35), Han 4.83 (91), Swi 5.10 (60), Han 5.23 (10)
Ziegler:
2016: Han 0,00 (3), Vaz 0.00 (2), Leon 2.01 (22), Hola 3.38 (3)
It's hard to draw any conclusions from these wildly unbalanced sample sizes over 1-2 years.