Faith: Healer clergy

Continuation of my project.

Some decades ago a plague to end all plagues swept across the lands... then again and again. Nations were decimated in the onslaught of disease and its tumultous aftermath. The kings that didn't succumb to the pestilence were toppled one after the other in uprisings and revolts. 
Such times caused many people doubt the unquestionable status of God and several violent cults rose from the fertile ashes of chaos. Still others were strenghtened in their conviction that God was purging the earth of sinners and non-believers. Although the church was reduced to tatters, with its wide networks of power, wealth and useful zealots reined by the iron fist of the High Inquisitor, it was the only institution to survive the chaos and swiftly rebloated in the power vacuum to control ruined cities. Still occurring outbreaks of the disease were brutally suppressed and any sign of impiety from citizens equally punished. 
The vast tracts of lands outside the church-controlled cities and farms, now called The Wild, were largely abandoned for the warring cults and roaming bandit gangs. Anyone living in The Wild was considered a heretic destined for summary execution...

The healer clergy "take care" of the afflicted. But if piety acts as a shiled, then why are they wearing those masks?