You weren't reading the patch notes were you? Nor did you read any other articles/news websites like Surrender@20.
Silences on Assassins were too strong. Riot said this.
Cho'Gath is not an Assassin.
His kit doesn't let him blink to your face delete you and blink away.
If you're unlucky at dodging his Rupture you will take a lot of damage but Cho'Gath has like the lowest mobility out of all the tanks in this game. There's only a couple that are just as immobile as him. TBH I can't think of any other tanks as immobile or less mobile than him. He can't just disappear and run away like textbook Assassins do.
Silences on non-Assassins are apparently okay because they aren't supposed to delete your face - granted that the silencer isn't superfed.
's bite isn't an ultimate. I don't get how you can compare them like that. I can't understand your logic.
Plenty of Assassins have been gutted in the past.
is gutted. He was an Assassin.
was gutted. He is supposed to be built like an Assassin.
was gutted with the DFG removal. He's fighter now because it's better than his assassin.
arguably got gutted. She simply got nerfed really hard because she was too strong for too long.
Bruisers are much much healthier than Assassins in this game; and I'm not talking about "Fighter" Trirelia.
Almost any champion can be bruiser/fighter. It's like the most basic role in League of Legends, it requires no real special tactics or difficult strategies like with ADC = Farm Lane phase | Support = Focus on peeling and healing | Assassin = Delete Targets quickly and get out because you'll die if you don't.
Bruisers and Fighters are simply the most basic thing to apply, build and play with.