I haven't seen Rengar do well at all since the nerfs.
 

If he's even picked in my games, anyway. I've yet to see an SotD Rengar, the thing that apparently is really OP according to GD posters.

Because Rengar is useless till you build like 5k gold worth of items... Hes like a Tryndamere basically

Riot realized this and they are buffing him
Also SoTD is gimmicky(once it goes on cooldown, Rengar becomes useless), but does give him incredible burst (though now people have realized that it's even better on Malphite apparently)