Tristana's rework helped change her from being exclusively a late game siege machine to a mid-game, reset-jumping daredevil that can burst unsuspecting targets at will. Prior to patch 5.2, Tristana was picked in ~10% of games, with a ~48% win rate. When the patch hit, Tristana's popularity skyrocketed to ~45%, and in the following week steadied out to ~18% - surprisingly enough, the higher pick rate and revamped kit unaffected her overall win rate at all.

These numbers tell us one of two things - 1) the balance team found a good middle ground between lowering values on most of Tristana's abilities while giving her new burst options as an AD carry or 2) players have yet to unlock all of Tristana's new potential. It's early enough after the patch that the latter option seems more likely, but only time will tell.

To better understand why Tristana's win rate has stayed static despite the changes, let's start by looking at Tristana's signature abilities that were altered only in scaling and base damage. Tristana's passive range gain per level has been lowered to 7 from 9, making her new level 18 range 669. This means Tristana won't outrage the staple long-range marksman, Caitlyn, until level 16 now - a feat Tristana used to be able to accomplish at level 12 with her old kit values. Rocket Jump and Buster Shot both lost some AP scaling, all but destroying the one-shot burst of AP Tristana with the joint removal of Deathfire Grasp.

Now, for the real drastic changes to Tristana's kit, the active ability of her Explosive Charge has been completely overhauled, while the passive component has stayed the same. The new Explosive Charge no longer applies a magic damage dot with grievous wounds; instead, Tristana throws a sticky grenade at an enemy minion, monster, champion or turret that detonates 4 seconds after attaching to its target. In that time frame, Tristana can increase the damage the grenade does by 25% per each shot she hits the target with after attaching the grenade - up to a maximum of 100%. This burst is HUGE if you manage to fully stack it.

The new Explosive Charge also deals physical damage instead of the old active's magic damage, and comes with incredible AD scaling to boot (1.1 bonus AD at max rank, up to 2.2 bonus AD when fully stacked). To complement the new grenade, Rocket Jump will also deal bonus damage based on the amount of stacks an enemy has on their grenade, once again, up to a maximum of 100%. What this means is that by level 13, Tristana has the ability to burst a target for 560 base damage + 2.2 bonus AD + 1.0 AP all from just comboing Explosive Charge and Rocket Jump. Throw in the 400 base damage from Buster Shot, and you can 100-0 most champions as a mid game AD carry over the course of 3-4 shots, all while having an escape that refreshes with kills and assists.

All that being said, while the damage potential for the new Tristana remains high from start to finish, it's unlikely the enemy will simply allow themselves to get in range of Tristana's grenade, eat 4 auto attacks, let her jump on the stacked target, and get out. It's no news report that AD carries get hunted/focused every chance an opponent gets, so a Tristana that starts jumping into fights without proper support will still get blown up by a team ready to pounce.

In short, while Tristana didn't change much on paper, her playstyle became much more aggressive mid game, while still retaining some of the late game siege potential she was feared for. Personally, I think Tristana is currently a top tier AD carry given the right circumstances. Due to her reduced ranged, Tristana struggles against poke comps, less her own team has pick-oriented champions (or a handy Braum/Yasuo to block Projectiles). Alternatively, if the enemy team is fielding a close quarters comp with an AD carry like Graves and several melee champions, Tristana should be able to safely stack Explosive Charges in fights, giving Tristana windows to aggressively jump on targets more effectively.

TL;DR: AP Tristana is dead, and AD carry Tristana has a lot of burst, but short range that makes her susceptible to poke.