Tristana needs to be given a proper niche
Currently tristana is a grab bag of parts from other hyper carriers(who she mostly predates) having weaker parts from each of their kits
She has less range than
when they have their steriods up, her only advantage is that her's is constant and with no draw back, but it is still less advantagous than what these guys have
She has a reset that is worst than jinx's by far, and even arguably worst than twitch's because he also gets a reset on his attackspeed steriod
She doesn't have as much aoe as jinx, or twitch and her wave clear is way worst than 
her dps is team fights is worst than litterally all of them
She isn't as mobile as 
she can't fight tanks mid game like

She can't defend herself like 
The only thing that trist can do better than the others is push turrets, but
is arguably better at that than her
Generalists aren't necassarily unhealthy to a role, Oriannia is a generalist mage that has been viable and rarely dominates the meta, but tristana shouldn't be one, or else she is going to have to be a weak champ,
my suggestion is to push her more towards the seiging marksman since she's the only one who has an ability that directly interacts with turrets, making her bomb stacks go from 30% bonus per auto to 50% on turrets would give her a reason to be picked over the others, since she can now turn seige situations heavily in your teams favour
) and even then the math might show up pretty good for her.
buffs helped her, but she still can't compete with all the AD casting early game adc's, that also scale really well with
late. It seems like things are about to start going to calm down with the
and