Let's Talk Tristana...
https://na.op.gg/champion/tristana/statistics/adc
http://www.leagueofgraphs.com/champions/stats/tristana
http://champion.gg/champion/Tristana/ADC
http://www.lolking.net/champions/tristana
She has a low play rate and is consistently middling to low in win rate. They gave her a tiny buff a few patches ago that helped her Q feel less clunky which kept her a float for a while but now she's drifting lower and lower on the win rate tier list. Part of this is that a lot of champions that counter her(Draven, Lucian, Caitlyn) are really strong right now and its absolute destroying her. She's had a lower than usual win rate for a while now, actually, due to Lucian's popularity and high win rate, only finally reaching a 50-51% for the brief window of time where he was absolute trash tier. There are also other options that scale better than her or do her job better that just are flatly in better spots(Twitch is currently outscaling every ADC, even Kog'maw, and he honestly should be looked at but there's also Jinx and soon enough, Kindred will eat up what's left of Tristana's one niche area of being the longest ranged AD).
The other part of her failing as a champion is the fact that, as an AA based ADC, she is far too CD reliant and has a build path that doesn't allow her to build any meaningful CDR. ER is a wasted item slot on her as she doesn't need the mana and is much more interested in getting her IE and AS Crit item as soon as possible; her AS growth as the game goes on is naturally lower than every other ADC as is her base AS in order to make up for the massive AS bonus that her Q gives. Youmuu's used to be viable on her when it still gave AS and it gave her some CDR that she desperately needed. And going Ionian Boots is just not an option as she needs the AS from Berserker Greaves; essentially, she can't go the CDR boots for the same reason she can't go ER.
A final issue that exists, I also feel like, is that over the the past two seasons since her rework, she has slowly lost her identity. When I started playing her in Season 5, I knew what my main's identity was; she was the best, safesty late game hyper carry. However, as the seasons have progressed and other champions changed, she's lost that niche to other champions. Caitlyn and Jinx are two of the biggest offenders here. Caitlyn offers the same late game hyper carry status with the same or better safety. Jinx sieges better than Tristana and doesn't have to wait 17 levels to get the same amount of range; she also has better AoE damage in teamfights, synergizes better with ADC items, and generally feels like Tristana without the jump.
And again, now Kindred is also encroaching on Tristana's turf as number one, safest late game hyper carry. Kindred is essentially a better Tristana in everyway with her current rework. Her Q is Tristana's Jump + AS Steroid + Runaan's all rolled into one nice neat package. Kindred's passive is almost a direct rip off of Tristana's current one only arguable, Kindred can make hers go even further than Tristana's ever could. And Kindred's ult make her so much better at dealing with divers than Tristana could even dream of.
I would really like to see changes of some kind to Tristana. I don't want to see her mire away in a gutter because Riot have continued to release and rework champions that just flatly do her job better and have stolen her spot. :/ I would like to see her be less CD reliant, I would like to see her passive buffed in someway so it could at least compete with Kindred's, and I would honestly like to see some AD items that she synergizes well with. Not even necessarily add more; just make it so that she has a legitimately good build path. People build Runaan's on her but honestly, its only so she can do more AoE damage in teamfights; not for any real reason like it goes well with her kit.
and
do that make her scale insanely well with pen + she has Q and ULT. Her rework wasn't "kinder" to her, they straight up buff all her scaling so that she can be a better AD caster with Q- ult and head shots(not technically an ability, but has same effect build and scaling wise).
since it's passive does physical, but even then, she only want's enough to break heavy armor. ALL of tris abilities deal magic dmg except the passive splash dmg on her E. She is an AS, and crit champ(like pretty much all Adc's used to be), but crit hasn't been worth a crap since the "marksman update" other then that short period where the static items were blatantly OP.