Percentage based weapon damage upgrades in abilities don't increase melee damage.

[snipufin]

Heroes like Bebop and Lash, who have "+X% weapon damage" in some of their ability upgrades, don't actually amplify melee damage, thus making this more in line with bullet damage. Meanwhile heroes with static weapon damage increases (+X weapon damage) do increase melee damage (although a +5.5 damage increase on your melee as Abrams is basically nothing).