Rengar Balance
Rengar is supposed as a assasin, hence the jg rework a lot before and his rework made him apart i mean riot said that they tried to have an smite for assasins and for champions with sustain, but it ended with purple smite on sejuani and so many builds that were not intended like rengar's blue smite, because he could burst a little bit more and is even in his recommended items, while he can not even sustain the jungle.
And for not to mention that when his normal Q gave him attackspeed, he could clear camps evenly with other jungles but only his empowered q adding attackspeed and having low sustain made him waste every full resouce bar in W because he would die to the jungle creeps, at least buff the healing or return the attackspeed because even tahm kench that is support has more sustain that a jungle oriented champion.