Riot, Talon needs some serious work. Have you forgotten that he exists?
Remember Talon?
He's that champion you created a few years ago. You last gave him a tiny patch in 4.18. Since then, it's like he doesn't exist. It's like you don't want to acknowledge his existence. People say that you like to pretend there's no such thing as Yorick, yet they don't seem to notice how bad Talon has it.
He's been untouched for ages now. The game has changed immensely, yet he hasn't been changed accordingly.
The removal of Crystalline Flask has really hit his early game hard. Now, a melee AD assassin, who has to compete with ranged AP mids, has a much harder time, and it was already hard to begin with.
His late game can still be decent (if he's done enough to let the game actually reach that stage) but he really does need some attention right now.
I suggest making changes to his passive, his W and his E.
Mercy (Innate): Talon's basic attacks deal 10% more damage to any target that is slowed, stunned, immobilized, or suppressed.
This is extremely lacklustre. Yes, it fits well with the theme of Talon, but that's about it. 10% extra situational damage is poor. He can't even take full advantage of it, because the only ability that slows an enemy for any useful amount of time is his W, which is generally used at range. I suggest something like this instead:
Talon's attacks mark his target champion. For 3 seconds afterwards, all damage done to that champion by Talon is increased by 15%. A champion cannot be remarked within 10 seconds.
I feel this would help Talon burst and trade a little easier, while preventing it from being on a single champion constantly would ensure he doesn't aim to prolong his conflicts.
His W, Rake, has quite a high mana cost during its early levels. As I mentioned earlier, the removal of Crystalline Flask has really affected him and his kit, with this ability being the greatest victim. Lowering the mana cost early on, but still having it scale to 80 mana towards the end, could help.
Changes to his passive would require changes to his E, Cutthroat, but it should be changed regardless. I believe it should work with his passive, amplifying damage done to a champion, when used on them, by 120% of his passive at the first level, up to 200% at level five. Increasing the slow duration wouldn't hurt either, but it may be too much.
Overall, the changes I suggested would assist Talon in focusing on one target (like an assassin should be doing). The previous passive was applied to any and all champions, a new passive would have him focusing on one, doing his damage and then dealing with the situation.
Ultimately, I think that something has to be done to give him an easier time in lane and the change to his W would do that. Altering his passive and E would give him a clearer purpose and assist him in what he needs to do.