Can we take a moment to talk about Sylus and the ability to steal ults

So what I can gather from this champion is that you click on a target and that gives you the ability to steal their ultimates with their respective cooldowns, surely this is broken, you could easily steal a champions ultimate with a short cooldown (Diana for example), shouldn't he have his own cooldown on the ultimate that is significantly longer, as his ult can change fights completely if the right one is taken