Katarina and Riven are easy to counter; being easy to counter doesn't mean said champion is balanced
CAUTION: Very long thread. If you don't want to bother reading it, at least do not post a comment.
TL;DR: Katarina and Riven are said to be easy to counter; this is only the truth during the lane phase. They are problematic due to things such as their lack of resources and the fact that they can snowball out of control. There are some champs such as Yorick which are hard to counter, and they are indeed so; but they have some weakness that make them lose most of their power once the lane phase ends
will soon be nerfed. With that said, on my opinion she is very problematic and not actually binary; if Katarina is ahead she is impossible to stop, if Katarina is behind, she can still get advantage of her bases and her passive to get back into the game. Due to her cast animation speeds, it's very difficult to react against her, and because of that, her reset passive, her high damage (when combining the damage from all her abilities) and her lack of any resource to manage, she tends to be quite "broken" at SoloQ, and sometimes even used at LCS (despite not being popular there due to teams actually having enough coordination to be able to properly stop her; I recall Katarina being used by Kami at a CBLoL match).
Katarina is also extremely stressful to play against, because you always have that in mind: "I must play perfectly against Katarina, else she will kill me and snowball out of control." Also, you are almost always in fear that your teammates, especially the bot lane, will be smart enough to back off if Katarina decides to roam to get kills and snowball if she doesn't manage to kill you during the lane phase (or even if she does). Also, everytime you lose against Katarina, you don't think "I lost because I let Katarina snowball even though I could beat her, so I deserve to lose"; you think "I lost because Katarina is a very dummy champion that Riot refuses to properly nerf".
With that said, Katarina is said to be "easy to counter" - Well, I don't think so. While it's true that she is easy to beat during the lane phase (There are numerous lane counters to Kat:
there are even more if you count champions that aren't commonly used at mid lane, such as bruisers) - the majority of the aforementioned champions are unable to properly stop Katarina during teamfights. Also, most of them don't match Katarina's roam potential; most of them are squishy; and most of those champions don't have an instant hard CC necessary to stop her ultimate.
Also, Katarina is resourceless, and unlike other "resourceless" champions, she isn't really limited by cooldowns, thanks to her passive. Most of the aforementioned champions are mana hungry, and they can even be beaten during the lane phase if Katarina manages to get them OOM. And the fact that she is resourceless means that Katarina can just do what she pleases during teamfights, and poke eternally during the lane phase, without having to worry about becoming OOM, for example.
Katarina is only easy to counter if she is a bad Kat, because a good Kat will not be so easily stopped by things such as hard CC, like everyone says.
Another champion that is just like Katarina is
. Unlike Katarina, she is actually easy to counter, but only with a few select champions. Riven shares the same problems as Kat; lack of resources and can snowball out of control. And a few players can fast combo with her Q, a trick that is extremely difficult to pull off, but makes Riven a lot more frustrating to deal with.
Even if you can beat her during the lane phase, you may not be able to stop Riven during mid-late game teamfights. For example, it's easy to survive the lane phase against Riven as
; you can sometimes even kill her if you play correctly, then you just stack armor and Riven can't kill you at all. The problem is that once mid/late game comes, Malphite just doesn't have enough damage to kill Riven before she is able to kill Malphite's teammates, and the only way that he is able to pell her off a teammate is using his ult, because Riven isn't bothered by the Q's slow thanks to her numerous dashes.
While it's true that Riven has a poor HP regen per 5, she can solve that by purchasing lifesteal. OR she can just all-in you before you are able to poke her to death. This and the fact that she doesn't have a resource to manage means that Riven is still hard to stop during the lane phase, and can potentially outsustain her counters. This is harder to do at top lane, however; at least when compared to what Kat can do at mid lane. This is because most bruisers aren't as mana hungry as mages.
Again, only a bad Riven is easy to stop. A good Riven, especially those that know how to "animation cancel" is actually almost impossible to stop.
The reverse is also the truth; just because a champion is hard to counter, does not mean that this champion isn't balanced.
Let's take an example:
. I can count on fingers the number of champions that are able to survive the lane against Yorick:
- and probably no one else. Even then, those four champions can still be beaten in some way or another, for example: against Cho'Gath, take advantage of his weak early game, harass him when he doesn't have enough sustain or tankyness to deal with Yorick.
However, Yorick isn't nearly as much of a deal, compared to Riven and Katarina. Why? Because he loses most of his strength once the lane phase ends. Yorick is forced to build items that don't make him tanky during early game, meaning that Yorick will be squishy during the lane phase. During teamfights, it's hard for Yorick to contribute with something. He doesn't have hard CC, neither he has overwhelming burst damage, which means that he will hardly be a threat during teamfights. Also, his ult isn't that useful. It is extremely good at team compositions where you have an hypercarry such as
or
or
but else, his ult has few good applications.
Yorick is only a force to be reckoned during early game because of his good base damage and massive sustain. And even during the early game, Yorick is vulnerable to ganks due to his lack of escapes. Meanwhile, Riven and Kat laugh at any attempt to gank them.