how about simply removing stealth from rengars ult ?
and giving it a bigger burst of speed it would still be used as it is but it would allow rengar to be actualy ballanced
even the name of the skill "thrill of the hunt" does not kinda synergize with stealth which actualy poses a lot of problems when it comes to ballance a)if riot will allow you to be aware of rengar ulting your team will just cling ot eachother and rengars ult is wasted b)if rengar is allowed to use his ult its 100% sure kill in most cases of its use
removing the stealth would allow riot to tap some power into utility elements, like leap range, movement speed, and ferocity gain
riot strugless to save stealth because they think that its all that rengar has, i think they should be proven othervise cause rengar has an amazing kit