So I just versed a Mordekaiser, first 15 minutes I dodge his E successfully almost keeping up in farm. Then Bam he hits me with 1 combo (E, Q, W) and my HP is a third of what it was (I was using Jayce), I then had to deal with his passive and auto attacks. He had crystal scepter and owned the lane without much mercy, even missing his E and hitting his q did a third of my HP later. It's honestly like versing a Garen that's half Mundo with GP barrel damage.
He's broken, Some say he is not however on the basis of champ difficulty, cc utility, damage and tankiness and mana (He uses none) he has hardly any vulnerability, apart from dodging his E and engaging on your terms or ganking him with a tank, which is a bit ridiculous.