Assassins I've played so far

Katarina is trash early game because, for some stupid reason, the ap ratio on her spin slash scales with level... She has like no damage early game outside her ult, but her potential late game damage is broken. You can Q-E-W to stand on top of two daggers, even if you're stunned or ulting, you will deal base + 2.0 AP AOE damage.

Leblanc got nerfed damage with delays added everywhere. Ult damage halved and cd increased in exchange of a 0.8 AP ratio delayed passive. Playing her is so clunky because of all those delays.

Talon is decent because of the AA-Q-AA instant combo. You can ult to get on top of them, then do the damage of 3 AAs in almost one instance, 1shotting easily after a . Armor pen (lethality) is trash now. Getting flat AD and infinity edgeis better as Q can land a guaranteed crit.

Fizz is utter crap, he was already shit before the rework, but they decided to halve his ult damage unless you hit it at max range, which is super unreliable. His W passive damage got nerfed, and the active got gutted. No compensation to his E CD or mana costs.