What is Cho'Gath right now?

So I just played a game as Yasuo mid against a Cho'Gath and i was able to solo kill him in lane 4 times. Well, surprise surprise he Solo carried that game. He built full armor and with 3 items had 5k health. So in my time of playing I've been told that the thing that mad Cho'Gath balanced was his ability to be kited, but when he is for whatever reason faster than your team, has thornmail and 3 moves that slow, with an ult that does upwards of 1k true dmg, i fail to see the downside of this champion. He can lose early, build full tank (unkillable), just run at your whole team and basically be tank assassin that can just free farm the adc, without any penalty. I feel that they need to make it so the more health he gets the slower he gets, it only makes sense. ALSO, i bought full items to counter a tank and i still tickled him. Its just unhealthy to the game.

ik this is kind of a rant but i still think there a nerfs that could be done