reasonable damage? her q bounces to 5 targets and can be triggered to deal more damage. fiddle's e bounces to 4 targets and has 15 less base damage at max level. granted fiddle's silences and has a longer range. but kat's takes no mana, has a shorter cooldown, more bounces, and also has a secondary effect that can do extra damage. (they have the same ap ratio)
only thing i can think of thats similar to w is malphite's e. Kat's does less base damage at max but has much higher ratios. though malphite's secondary effect of slowing attack speed is more helpful to the team, but that only really helps against people that rely on attacks per second. which isn't really a whole lot of champions. whilst kat's movespeed can be used to chase and flee a fight. also kat's w has almost half of malphite's cooldown, takes no mana, and almost has 100% more range.
kat's e and talon's are kind of similar. talon's e doesnt do damage, rather it just amplifies and basically has a .25 second snare. at max rank talon's e will fully nullify kat's e, before that kat's 15% damage reduction is pretty superior. However, kat's reduction is half the time of talon's damage reduction. however, id say due to the fact that kat's has damage it at LEAST nullifies this difference. the damage is 160+40% ap which i think is greater than the amount of damage talon can do in 1.5 seconds. they actually have the same range, however once again, kat's does not take mana AND can be casted on allies AND kat's is almost half of talon's cooldown at max rank.
still think she doesnt have damage?
wrecks Kat on the daily, so I don't see why Kat should have mana or any changes at all, she not that hard to beat