I find getting an S as Jg next to impossible anymore. My kill ratio has to be in the double digits with few deaths, my warding well over a dozen, my deaths kept to minimum or 0, my CS above 100 (despite most of it being EPIC monsters), and my damage to enemy champions 30k+ to even qualify for anything above an A+. And it's even worse if you're playing a tank jungle. You could do the best you've ever done in a while as a Tank and then end up with a B+! The game doesn't even seem to account for you slaying dragon and baron anymore.
It was so much easier for Jg to get an S with Devourer in game because the game considered that a difficult objective. Now that it's gone, there is no easy button for jg. Meanwhile, in bot lane, support can feed out the ass, throw the game, and still get an S-.