Well batting average alone is certainly a stupid way to judge how good a catcher is, but...
Sean Murphy, Oak: .221
Martin Maldonado, Hou: .181
Victor Caritini, SD: .211
Yasmani Grandal, CWS: .190
Mike Zunino, TB: .203
William Contreras, Atl: .215
Austin Hedges, Cle: .155
Colorado is splitting their catching among
Dom Nunez, Col: .160
Elias Diaz (yeah, that one), Col: .197
Seattle is splitting their catching among
Tom Murphy, Sea: .192
Luis Torrens, Sea: .205
Those guys are all in the top 30 of at bats by catchers.
If you make a list of the top 30 catchers in baseball right now including everything that goes into the position, Jacob Stallings is on the list. He isn't in the top ten, but he probably isn't in the bottom ten either.