Other then Leon being super-human, the real on the surface surprise in the catching situation is that Hanigan is being put on the major league roster. Hanigan, the same player has looked like a deer caught in headlights when catching Wright, and whose batting line (.186/.250/.229/.479) actually makes Vazquez' batting statistics look relatively good.
So the hope is that Hanigan regresses positively toward his career numbers at the plate and gives us more than Vaz even when you factor in the downgrade in defense. I think the upgrade in offense is extremely unlikely to balance off the downgraded defense. I think the RS know this and Hanigan is being put on the roster to show he is healthy, and show he can hit more in line with his career OPS of .683. In that case with his team option for 3.75M next year, he has some positive trade value at least to a team whose starting catcher goes down. Maybe with some other minor piece, he can fetch a 7th inning reliever type.
To me, the move is not because Hanigan is such an upgrade over Vaz, but rather doesn't represent a tremendous fall off, allowing Vaz to be stashed and hope that Hanigan can establish some trade value.