I just realized how low Mantheon's damage actually is.
I was top and my enemy was a TP/Ignite Mantheon. I picked Morgana top. His damage on me was really low, and I backed when I was low so I wouldn't trigger his 100% crit on AAs and Q. In the midgame he used his full combo on our Jinx and it was only 30% of her HP. He might as well have been a minion at that point. Never seen a more useless champion, it was kinda sad.
So, here's the solution to lane bullies. Morgana and play like a wuss early. You'll be able to get farm later and even if you don't you're still a threat.