Why i feel like Qiyana isn't an assassin but more a fighter ?
Honestly, as an assassin, she is really bad.
I don't say the champ is bad, but on her role, she is bad.
She isn't made to be an assassin, not with these actual dmg. And even with buffs, she wouldn't be an assassin.

What are their common point ? Huge mobility, huge dmg on a single target. All of them can execute safer than Qiyana.
Qiyana only safe tool is her Q under grass enchantement. The invisibility will protect you for some dangerous situations but otherwise, you can't kill someone and temporise or replacing in a safer place.
All of them have a better burst than Qiyana. Let's be honest : Do you really think Qiyana make dmg ? Zed is able to kill you with one
and W R E Q + AA.
Talon press W + Q + AA with ignite and delete someone at lvl 2.
Rengar jump on someone from an huge distance (compared to Qiyana minis dash) and delete someone.
Kha'zix jump on somone from a long distance and delete someone.
Fizz press R W Q AA and dogde your spell while damaging you with E too.
Diana press Q W R E R and you are death.
Evelyn put her W, place a E or a Q and R.
Katarina is a little bit different, since she is an assasin made to pentakill. Her reset are what make her better than Qiyana.
Leblanc delete someone with E Q R W.
Wukong build with lethality, become invisible with W, E Q R and delete you while bumping your team.
Akali harras better in lane, have better dmg, mobility... She can temporise...
And
?
A small range, small dashes... How you can get to the enemy adc ? You have to told me how you do because if he gets protected with a frontline, it's not with 2 ridiculous dashes like this that you will reach him. Imagine a Cait. You think Qiyana is something to be afraid ? A Zed can reach her way faster, way safer and delete her instant. A Qiyana ? Hahaha, i shoot her down in less than 3s before she reach me.
The only thing Qiyana has compared to others is CC on her ulti and her Q if enchanted by ice. But it's short range.
But it's isnt a big deal since she will place this stun on the frontline and not on adc/mid laner.
She don't have protection and she is squishy. So she can be zoned easily if she isn't under her Q enchanted by grass.
Players play her with
...
Is that assassins items ? Lethality build isn't good on her.
Why i think Qiyana would be more good as a fighter :
First, the build you make on her. It's like Irelia one and it's not really assassin.

Her W passive give her 20% AS and dmg on AA which is useless as assassin because your goal is to burst and not to do a lot of AA.
Since she lost her passive AS and dmg on AA when she use her Q, what the utility of giving this if not to makes her a fighter ?
She isn't busted enough to be an assassin. It's not a bad point, as adc main i'm not vs Qiyana because she is less a treat to me than Zed, Pyke, Rengar, Kha'zix. But let's be honest. She can't reach someone fast as a real assassin and that why she would be better as a fighter because of that.
Her ulti is a good spell who make her useful in teamfight but not in way an assassin would be.
And her personnality and her character don't suit an assassin role.