I tried this in ranked today and got absolutely DESTROYED by a jungle Hecarim on the other team. It was one of the most aggressive Hecarims (and mid lane Akali who would come with him) I've seen. He got first blood double ambushing/chasing me in the jungle, took nearly every buff, might have had them warded as well, was flying into lanes, and practically took no tower damage since he was 3-5 levels above the rest of our team. He would tower dive 2 or 3 people, literally run behind the turret, into the jungle, maybe back through the turret, and out into the lane without anyone being able to stop him or do much damage.
In summary, he was doing the things junglers are supposed to do, and it's probably my worst role and did not work out well.
I was maxing W though, which gave me even less damage if he tried to catch me in the jungle. Maybe the right strategy would have been to max Q once I started seeing counterjungling. I just kept trying to farm, and buy tank items, and occasionally push lanes or towers to get closer to his level, since I stayed 3+ levels under him.
HOWEVER! All that said, our top lane did okay, our mid Cho stayed big and strong and did not feed Akali tons of kills, and our bot lane got kills, some of which I may have even helped with! And after all the Hecarim diving, and taunting us in all-chat, he dived into our team maybe twice 30+ minutes in, resulting in two lost teamfights, and us simply taking the nexus the second time. And of course he blamed his team. I can't credit jungle Nasus with the victory, but it was incredibly satisfying to see a taunting, arrogant, aggressive player lose.