Feels like it's been forever since she's been even a semi-contested ADC pick.
Does her ult need to do more damage? In theory her kit seems to be fine, maybe she just needs a bit of a tune up? A slight change to help her early game maybe?
They fucked her up with the adc rework
needs an LCS player to play them
The reason they cant just buff her is because one mistake and she would become a monster who killed everyone before they even got close along with a rocket reset its really scary to think that one buff to strong she would be so disgusting so Riot is probably keeping distant
needs to be nerfed first. If she isnt banned, she's in every single game.
-edit-
And I'm sure someones going to say she isn't OP. No, not by a longshot. However, she's undoubtedly the strongest and safest pick for your bot laner.
All she needs to be brought in line with other adcs, is removing the trap/headshot interaction, or at least reducing its damage. It's just too much. Even with tanky supports, you're going to lose a quarter of your HP just trying to make sure your allies don't step on the traps. It's far, far too much.
She's relevant right now, just not popular/fotm.
Currently she is more about taking towers. People are more interested in killing to worry about towers, so she sits in the back to Lucian etc. She is still very strong. However, she also pushes the wave...... Which is good unless the enemy jungler likes to capitalize on this.
I use her as AP and AD, mostly top and mid because i hate adcing..... But all she needs to become a monster is 3 items for her AD side.
Blade of the Ruined King = sustain, attack speed, damage, current hp damage
Phantom Dancer = att speed, crit, move speed, and decreased enemy damage.
Bloodthirster/Infinity Edge = massive damage boost with either increased damage potential or sustain (IE for adc, Blood thirster for Top).
She out ranges almost everyone pretty quickly and has that increase added to her E which she can use in the middle of jumping at the enemy..... Potentially getting an auto off mid jump after bomb too..... Rapidly procing the 4 shot explode of the bomb resetting the jump.
Caster's have to much wave clear/ harass early on 
Which with Tristana's that max E it always hurts her being pushed in and makes her lose lane without the ability to win.
Measuring by health and regen we see 543 health 6.19 trist 5.40 6. jhin 524 5.67 cait and 518 5.67 jinx On paper it would seem that this would be decent. However Ignite range 600 Exhaust 650. With exhaust being nerfed more I've seen more and more supports taking Ignite. If the range is 600 and the casters may attack farther than 600 then they don't put themselves in danger, however back in the day casters also had decently high mana usage lke a ezreal needing a tear same as varus. Though these champs don't need one they can go straight damage and not need to worry of that. Not to mention their exists tricks like Caitlyn Flash E which will be the death of you as she has 1300 ranged auto that there's no way to outplay.
Thank gosh for 
It's literally a blessing for marksman's
A proper rework is what she needs.
