When Kinetic Scream is selected for Warcry, an estimated damage figure is provided that appears to be 2-3x higher than the damage it actually deals. This may or may have to do with also having Jormun’s Wrath. Additionally, the
tooltip states that Attunement scaling only affects mana efficiency and not damage (which given the observed damage may in fact be true). To test, I traveled back to the Divine Era with a level-14 character and entered the Fortress Gardens, on the theory that damage reduction would be low or nil there.
Screenshots: https://imgur.com/a/YLeHYok