Wrestling Mastery will be receiving a Mana cost for each hit delivered that benefits from Knockout's passively increased damage. I don't exactly agree with this one. While Wrestling Mastery does significantly increase melee damage against low Resists opponents, the damage difference isn't as high against high Resists opponents (to where Armor Ignore or Inferno/Conductive Blast/Rune Corruption would probably be a better option against higher Resists opponents).
Did some more testing with Wrestling Mastery, and i was correct, the difference isn't near as large against high Resists opponents. When testing Wrestling Mastery on a 0 Resist Drone, the Wrestling Mastery Iron Beetle was able to hit for up to 80 points of damage harder than the non-Wrest Mastery Fire Beetle (both had same STR/Tact/Anat/Base Damage).
Against a Eternal Gazer with 66 Physical and Fire Resist, the Fire Beetle was doing 16-22 damage a hit, and was doing 40-48 during Rune Corruption, AIs were doing 60-70s damage. Against the same Eternal Gazer, the Iron Beetle with Wrest Mastery was doing 16-35 damage a hit.