Issue with this mechanic of hers is that she deals almost no damage on targets that can move out of her range though, while her DPS on tanks is absolutely good it's also the requirement for that DPS that makes her so unable to handle anything with mobility.
She needs to slow them, and since she´s so squishy she has to run if someone get's near her, thus she has a terrible affinity for assassins and divers who reduce her to doing nothing except running.
Meanwhile playing a tristana instead let's you knockback the assassin and auto attack a few times and they die, or even Varus to root them and then auto attack and they die all the same.
It's only Ashe, kalista and kog who DPS properly, but Ashe has the worst requirements for DPS and kog always comes with a lulu or a Janna to keep him safe anyway.
So it comes down to comparing the DPS'es to eachother Ashe,kalista, kog and varus.....also, vayne.
Varus can go DPS builds but he can also run the static build which undoubtedly is immensely powerful, 10 times so when snowballing. His poke is great and engage potential is only slightly inferior to ashe, and while his lategame isn't as great you rarely get there anyway.
Kog runs at his own pace(rather slowly) but as a compensation he get's to DPS quite freely as long as he can use his W. And since no sane soul would ever play him without a lulu or janna to help he's pretty much great.
Kalista has somewhat bad range but her kiting is good compared to the others, but the real kicker is her E that keeps her going strong.
Then we have
.....this is a abomination that i don't like at all :(
Then finally we have
, she is just as immobile as kog is, lacks his damage, doesn't have good poke (100 damage x 5 times then outa mana lulz) has good engage potential but kinda low CC until she stacks enough crit chance and she needs 4 auto attacks first before she can activate her damage steroid....that isn't all that good without enough items.
.....yeah she really isn't all that great.......and did i mention that her early game is kinda awful too?