Do not revert Rengar.

Being killed in less than a quarter second from stealth is not fun and will never be fun. Rengar is annoying as shit to play against when he has that play pattern.

Rengar is fine. Newer players will struggle with him sure, but one tricks and experienced Rengar mains are finding good success with him. His winrate has been steadily climbing in the past few patches, and as you look further up the ladder he's winning more and more. All this tells me is that he's a difficult champion to play successfully, but buffing a champion who requires finesse so that even bad players can find success will make him broken at higher levels of play.

Ryze syndrome, basically.