He's at a 48% winrate. Not only is that not unplayable, but it's actually 2.98% played so really that's as close to balanced as rengar has been in probably forever. I'd say that rengar doesn't actually need any changes right now, because the moment they nerf one of the problem junglers, zac for instance, rengar would be getting an indirect buff.
There are more of you losing their than their should be. When I mained akali, riot said they were reworking her even though her numbers weren't insane at all and her winrate plummeted 7 percent. Just now I'm dealing with corki's winrate dropping 6 percent. I'd kill to have corki be decent enough to break 48% winrate.
Basically, rengar is far away from unplayable and you guys are overreacting as fuck.