Quick question about shaco

How come when in the patch notes it says that the balance department doesn't like how he can burst from stealth, yet the keep the stealth time and gut his damage and force him to a bruiser role? Also if i may add, how come riven's ability to wait in a bush for a minute or two, pop someone like a zit, and walk away considered balanced and when shaco does it, it's considered crazy broken and unbalanced? I know that shaco needed the nerfs but reducing the stealth on Q instead of taking the damage would've been more than enough in my opinion. I'd just like a rioters opinion maybe and a discusion can form about my beloved dead champion