This habit kinda continued with me to the Rift, but when I play Tristana, always enjoy running Lethal Tempo. This is because of the value it gives me throughout the game. Sure, she can't stack her E super quickly or do a level two all-in, but what does that matter when your playing ARAM? It's much easier to snowball since you're with your team constantly, and it also makes trying to play solo that much harder and riskier. ARAM all but eliminates having the opportunity to 1v1 burst someone level 2 or 3, so not running Hail of Blades isn't something I'm particularly bitter about.

But Lethal Tempo, however, is much more useful. Unless there's an assassin, more often than not ARAM teamfights are front-to-back, meaning Tristana spends more time using Explosive Charge and Rapid Fire just as means to auto-attack, with Rocket Jump mostly being reserved for post-teamfight clean-ups or follow-up for engage. And with the bonus range Lethal Tempo provides, in combination with Draw a Bead's bonus range, you'd be surprise by how far away and fast Tristana can lay down damage in the later stages of the game.

Triumph and Legend: Alacrity are just supplementary, they can be exchanged for the others if needed (though I'd recommend keeping Legend: Alacrity for the AS :D

Sudden Impact works well for extra damage on Explosive Charge, and Treasure Hunter's good for the gold early and snowballing but honestly they could be subsituted for something like Gathering Storm and Absolute Focus to help out more mid to late game. And if you want to go for a bit more lifesteal, Overheal and Legend: Bloodline work nice as well.

Like I said before, I've tried the Lethal Tempo and Hail of Blades builds. Usually I build Trist just ADC though (I did once do ***sassin using Hail of Blades, but that was when Duskblade was still around and made it easy to kill someone, go invisible, and then Rocket Jump back to safety or to get chained kills).

So if you've ever tried anything "unusual" on Tristana in ARAM or you tried one of my builds, let me know how it goes in the comments, hearing experiences with the builds and/or pointers on how to refine them would be awesome as I explore the many ways to use Trist on the Howling Abyss!