Yeah, I'm so sick of seeing Swain in the LCS. He's so stupid good and just wins every game he doesn't get banned in...
OH WAIT.
Seriously, I know LCS isn't the only metric by which we should judge the game/champ, but I can't think of a single time Swain has been picked in a professional match (I'm sure he has, you don't need to prove it to me, the point is its is incredibly rare). That says a lot.
I'll admit to not having a lot of experience with the match-up, but he should be pretty easy to pick into. Just about any champ with a dash type ability, or anyone who outranges him. Ziggs has both of those. Fizz and Kat both have a dash AND grievous wounds, so those should be easy victories. Syndra and Xerath also probably have an upper hand in that it should be hard for him to close on them to land his snare.
If he picks into you, first, good for him. Second, you can still take ignite, and/or buy Morellonomicon to counter him. Grab a bunch of potions early and just farm for your life. If he wins by counter-picking you and then capitalizing on that, well, it happens.
And before you counter that you are only complaining about the people who play Swain, don't bother. You wouldn't be complaining about them if you weren't losing to Swain. Learn to win against him and it wont matter how easy he is for people to play, or what those people say.