DAMAGE REDUCTION: Which ones are best for rat runs?

Ranged Affixes
Mortar
Fire Chains
Electrified
Thunderstorm
Frozen (explosion)
Jailer

>> Ranged affixes that are most dangerous (1) proc even when monsters are frozen, (2) deal lots of damage in a short time, (3) are hard to avoid. Ranged damage reduction is VERY valuable and should be rolled on Chest Armour and/or Bracers where possible.

Melee Affixes
Frozen (ticks)
Orbiter
Arcane Enchanted
Vortex
Reflect
Wormhole
Plagued
Poison Enchanted
Frozen Pulse
Desecrator
Molten

>> Most melee affixes only spawn when monsters are not frozen immediately; therefore, melee damage reduction is LESS valuable on speedy rat runs

Reduced Damage from Elites
Calculated last
"Elites" include blue packs, yellow packs and Rift Guardians
Effective against all affixes EXCEPT Frozen Pulse & Molten explosion

>> VERY valuable property and should be rolled on Chest Amour when possible

tl;dr: Reduced Damage from Elites > Ranged Damage Reduction > Melee Damage Reduction