So uh, tristana AP...
First things first : I love the work you did on Tristana in terms of visual. Now she truly has an identity and doesn't look like a potato with three lines 
On the subject of gameplay...
Tristana AD feels less passive than before, which is reaaaaally reaaaaaaally great. But AP tristana.... what happened? I agree that she was in a truly awful spot (never bought a DFG on her cos' i was one shotting people anyway - nuff' said) but right now, I actually think that she lost much to the trade. I mean, the whole kit revolves around her "e" and the combo that you can do with it. But how do you use it to its full power? Via auto-attacks. That's where the whole problem is.
It's extremely hard to go to four stacks which would be totally fine if we were talking about the old trist'. But with this one, she truly hits like a baby, unless you get her to the full four stacks. And use your w on the target. But how do you get to that point? Auto-attacking. Which is clearly NOT a good idea in a fight between mages or when you're suppose to kill a squishy who hits as hard as a marksman. Plus, the window of time to go with four stacks + place your w is shorter than ever. Plus, the guy who got e placed on him has two choices : go full ham on you (you'll die or waste your ult - not exactly fun) or just... leave your range. Aaaaand you'll deal something like 80. Aaaaaaaand he'll laugh and what will follow won't be fun.

What should change with her e? Well actually, I think that i'll want to hear the community on this one (please try to avoid the - oh so classic - "just change back to the old one lol")!
Love ya all,
Reiquai