the wicked avater card ruling?

ok si im in a duel with this guy and he xyz summons into gagaga gunman and i have gorz and the wicked avatar out. he attacks my avatar and i said he takes 100 however, he states that since the eff of gunman happens during the damage step the wicked avatar doesnt recalculate its own attack damage. does anybody know?

Avatar's effect overrides everything from what i can tell, good thing to point out though, But yea Avatar over Gunman

thats what i thought after i looked at the examples in the card rulings but there wasnt anything specifiaclly on damage step effs

the avatar calculates its eff based on the opposing monster's atk+100
in other words youre right

yeh it does shining but based on the damae step would its effect be fast enough? im guessing since its eff to gain the highest attack is continous it would resolve last for those types of situations and basically still be at 2800 because of me having the gorz out