OP = Toxic = Lack of Counterplay?

I've been curious what this(title) actually means and what Riot's logic on nerfing certain champions. They've nerfed assassins and mobile champs a lot this season, and I'm not quite sure why, unless they want to remove the concept as a whole from the game.

Kassadin nerfs pretty much made him unviable, Akali was fine (IMO) to begin with, etc Yet Leblanc will do what both the above do well but in one package. AND she has a snare, which neither the above have (a hard cc i mean) AND her damage is way greater than either. Not saying she's OP, but Riot's logic doen'st make sense (IMO)

I'm going to list some examples on who I think is OP and why. Before you downvote, please give feedback. I'd like to know what you all think.

Xerath He's a long range burst mage. He can kill you from half a screen away, and has a stun to get away. I get that that's his role, and nothing wrong with it, but my grip is the lack of counter play at all stages of the game. With the recent nerfs to mobile assassins, Xerath has become too strong since he can sit back and burst without fear of being killed himself.

Obviously nerfing his range would take away from his core, but a few nerf suggestions I had

1. • Negative scaling on his Q (As he increases range, less damage it does) That way he has to make a decision whether to do more damage or be safe
2. • Lower base movement speed

Heimerdinger His turrets are too strong. I think his other abilities are fine, just his turrets are way too OP. He always seems to have his turrets off cooldown. As a result, he never has to decide between using his turrets to push or to use them to defend himself/attack opponent. As a pusher and a mage, he should have to smartly balance the use of his turrets instead of spamming them whenever he wants.

Nerf suggestions

1. • Increase cooldown on turret creation (so he doesn't always have 2 or 3 up at once)
2. • Increase cooldown between turret casting
3. • Turrets die when he dies

Vi, Malzahar, Warwick I think these champions are good, but not necessarily OP. But I do think suppression abilities should be skill shots.

Annie Burst, CC, too easy to use.

Nerf suggestions

1. • Make Q a skillshot (and only count it has stun stack if it hits enemy)
2. • Delay on Tibbers (enough where you can dodge, but requires timing to do so)
3. • Allow her to put her E on ally champion (she's support after all)

Udyr Dear god please nerf his movement speed on bear stance. Impossible to run away or catch unless you burn flash or have escape.