The Laughing Storm is a bomb of a card, whether you think he is broken or not, I think everyone agrees he absolutely raises the bar on the power level of House Baratheon.
But I have to wonder, is he really more powerful than the other defining characters for the other houses?
The Red Viper (PotS) - If you don't have a way to deal with the Red Viper, it can be game over real quick for you.
Wintertime Maruaders - Singlehanded wrecks boards like no other character
Castellan of the Rock - easiest repeatable kneel (control) in the game. If you don't deal with him, your board is crippled turn after turn
Blackfish - Draw and powergrab? You better get him off the board fast or lock him down, otherwise you will find yourself losing fast.
Obviously I didn't mention Targ. They currently lack a true bomb character. I very much like the Khal Drogo who kills during power challenges and I think he can really alter a game, but apparently nobody uses him, so he doesn't count.
So while TLS is awesome and will alter games, I'm just not sure I see him as that much more impactful than any of the other game altering characters for the other houses.