This seems really weird to me. Both Diana and Rengar can one shot you by the time they reach lvl 6, the thing is, Diana has to land her Q and proc her passive in order to effectively one shot you. Whilst Rengar just needs to press R and Q and you're dead before you can even blink. (not exaggerating)
Rengar is such terrible design lol. Champ has been a design problem since its release some years ago.
Hard disagree. Rengar is an awesome champ that a ton of players love. Also does an incredible job of delivering on the thematic of a stalking hunter. Reliable burst damage is an important part of league that keeps the triangle of burst vs. sustained vs. tank vs. burst in line, even if it's frustrating at times to get popped by a fed alpha-lion.