I still don't understand why Rengar tells you when he's coming

I mained this champ in Season 3/4 and the whole joy of playing him was sneaking up on people. Now he's less sneaky then kled and you're not even invisible. What's the point then, I can play literally any other Assassin like Zed or Talon who not only don't tell you when you're coming, they do more damage too.

Also what's with the way the new bone tooth scaling works. The last stack alone is worth the same as the first 3.