Rengar ultimate
I believe that rengar is a bit weak without his stacks of course you just need to be smart about your ability usage although when in solo q a surprise team fight arises you could be completely useless. Although, buffing his cooldowns would make him too powerful so I suggest that an altercation to his R ability would be the right choice to help his team fight potential, since his assassination abilities has been destroyed. So to make his fighting power better make his invisibly be uninterruptable and happen much quicker.
MAKE HIS ULT NON INTERUOTABLE AND PRETTY WELL INSTANT
Thank you for reading. Sincerely, HurryJerky