The Vindictive idol prefix (30%-80% increased melee damage for 4 seconds after a skill echoes) doesn’t look like it’s working. I got nekkid & equipped a white melee weapon (an Iron Mace with +28 melee phys damage if you’re interested) & had minimal increased damage from passives (+56% increased phys from 8 points in Sorrow & Steel & +20% from Relentless). I was using the basic attack (as it doesn’t get any increased damage from strength but can still be echoed).
From 37 attacks my average damage was 53.8 (min 44, max 63), equipping the idols (a +78% increased melee damage for 4 seconds when a skill echoes & +38% increased melee damage for 4 seconds when a skill echoes, so you’d expect something like a 116% increase for 4 seconds after a skill echoes), however my average damage for 2 hits after the attack echoed was 53.8 (min 44, max 64). I would have expected something in the range of ~90 damage after an echo (or 116 if the damage after echo was multiplicative which I don’t think it is given the wording).