Deflection is a Paladin (first tier Retribution tree) talent. The talent grant a 1% increase to parry chance per point spent.
Tankadins will find this talent even more important for them because it is much harder for them to attain uncrushability than warrior tanks. 5% parry from this talent is a big help.
On the other hand, it is much less useful for Retribution Paladins for similar reason as DPS Warriors.