Well... That's a Thing
Apparently Riot has decided to put onto the PBE a change that makes Katarina's ult cooldown scale with level. Currently, it's 90 seconds at all ranks. With this change, if it goes live, it will be 135 seconds at rank one, scaling down to 15 seconds at rank 3. I'm a Katarina player and even I hope that these changes don't ship because they're just too strong.
Let me just explain why this is busted. First off, her passive - Voracity: Any time an enemy champion who was damaged by Katarina in the last 3 seconds dies, all her cooldowns are reduced by 15 seconds. I don't think I need to explain further: once Katarina is level 16, every single kill or assist will reset all of her abilities, including her ultimate. This means that, well, RIP anyone who tries to fight her in teamfights.