I have a friend who plays jungle Rumble since Season 5, he's still having success with it.
Meanwhile, I've found a hero in Pantheon and Syndra. Syndra especially is disgusting: get 3.6 Magic pen from masteries at level 1, and then another 7.83 magic pen from runes. That's 11 magic penetration from the get go. At level 8, you'll probably have completed your Sorcs, so you're looking at 3 + (8 * .6) + 7.83 + 15 = 30 magic penetration! With how little people buy magic defences, and with how easily Syndra can initiate with Q+E or W+E, she feels incredibly strong against whatever she's fighting.
Pantheon, meanwhile, just lobs his spear at his opponents and bullies them out of the lane endlessly. Due to building Youmuu's, you're looking at 20 + 7% arpen... and I usually get a Maw of Malmortius for all the magic damage. That's 30 arpen! Everyone shall feel privileged to die at my (ridiculously oversized) feet.