The preseason patch has kicked in, and the two Rivals are currently insanely unbalanced
as an AD player I thoughly enjoy being hamburger with legs vs all the Rengar and Khazix right now
— loco (@Locodoco) November 13, 2016
Both Rengar and Kha’Zix are the strongest junglers in the moment, and maybe even the whole game at this point due to certain changes in the pre season patch. Not only did these champion get changed (buffed), but the removal of the pink ward to control ward has only increased their power.
The control ward will be able to spot Rengar, however, due to the changes that prevents it from spotting invisible champion, the purchase of the item has decreased. Rengar is also pretty much left unaffected from the camouflage change, since Rengar does not require to walk in auto attack range of the champion in his ultimate, since he leaps to them anyway.
Kha’Zix on the other hand is absolutely insane since control wards will be unable to spot him once in ultimate, or coming out of the bush. This means that it is impossible to target Kha’zix with a spell, and the only way to hit Kha’zix would be to cast a spell in the direction Kha’zix is in (total guess unless you red trinket).