I'm also trying to figure out this question too, in most my games enemy ADCs usually get ahead of me somehow from out of the blue with more gold and items(EX: Twitch and Vayne), the only way for me to kill them is with a Support with strong pokes and CC(EX: Brand and Sona) or jumping out the jungle and Assassinating them when they're at low health, while they go around solo killing my teammates all willy-nilly. Is she suppose be like Ashe and have higher assists than kills?
I don't think Tristana changed much, 2 secs added to Q(So you can shoot faster for alittle longer, that's not much since it don't do anything else while Kog'Maw can do the same, but better because it has damage ratios) and magic resist was added(everyone got magic resist it was mandatory, the plus side she takes alittle less damage from magic damage, the negative side she does less damage since all her skills are magic damage so it's just a balancer). IMO I think people is looking at the wrong person, it's not Tristana who is strong, it's her Supports(alot people don't believe it but they do have a big impact on the ADCs and team success).
Her skills don't have burst because she only have AP ratios except on E(which takes too long to stack that is why she builds alot of AS for compensation when her Q is down).
Her ult doesn't have a high chance of killing you like most ADCs.
She has no synergy with the items she commonly builds.
Her only strengths are pushing, taking down towers, and late game range. Everything else she does is lackluster.
Honestly I would like if Riot rework her kit or at least tweak it, in the future.
The boards are filled with bunch of sheep on wagons bleating together, because of what they saw on the LCS and needing to express their hatred. Most of the complaints you will see is about her W jump(used situationally with resets which is conditional) and her Ult which is mostly use defensively(Poppy and Tristana practically have the same Ults with the same weak damage attached).