The problem of monsters shotgunning players at close range has been discussed before: [1.0.0.8] WTF is going on?
The solution was thus: Grim Dawn Version v1.0.0.9:
But, I don’t know if this change was applied to Valdaran’s aura.
With respect to this aura, the major change between 1.1.9.8 and 1.2 was that the RR was removed but the lightning damage from the projectiles was increased by over twice as much. This can be verified in GrimTools because you can switch between 1.1.9.8 stats and 1.2 stats at the top left.