Like other similar effects (aura granted by item but not an aura skill granted by item), the aura buff won't be affected by any of the player character's aura bonuses, however, the effects will stack with other party members also equipped with Leer Cast. However, since the item also has another mod 30% reduced Damage the net effect would be 15% reduced Damage for the player character and 15% increased damage for the nearby allies. increase/reduce mods are additive to each other.
+(20-30) to Dexterity
30% reduced Damage
+(20-30) to maximum Life
+(20-30) to maximum Mana
You and nearby allies gain 15% increased Damage
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