Mordekaiser was fine before the patch, Mordekaiser is pretty meh after the patch, still i get called OP when i score 20/1/14.
So, my dear whiners, its time someone taught you how to fight mordekaiser, so riot doesnt have to ruin him any more.
Mordekaiser can go two basic routes. damage or tank.
if you see him go tank, he can go either for MR or for armor, depending on YOUR team comp (you really dont want to have all AP or all AD team, really)
If he goes tank, gank him early, pre6 he is just paper, not a tank. if he goes for Force of Nature first, make your AD carry gank him, if morde doesnt back to a turret, he is DEAD.
if he goes for thornmail/randuin or some other armor item, use your brain and let the casters IK him. if he goes for hp..... meh.... that just means he doesnt use his shield.
If he goes dps, gank him early, pre6 he can just harass with E, and thanks to you whiners, he cant even gain shield properly from hitting creeps. If you are stupid enough to let him farm the creeps and even let him score a kill (using the turret of course, morde just doesnt have the dmg to kill anybody with brains), use your CC to kill him, anywhere
the main question is "why didnt i kill morde when i pressed my QWER and hit him?!"
the answer is "the shield absorbs the damage, he gains shield by dealing damage with abilities, dont let him get the shield" "and why you omg so clever noob?" "just choose, exhaust, stun, silence, knockup, ignite (makes his selfheal, especially with ult lower), snare and kite, slow and kite, wait for him in bush before he gets the shield, dive him as a tank, maybe i will remember some else, there are just so many ways to counter him..."
If you are so dumb to let morde get his shoes, hextech and lichbane, you are probably doomed, because his Q does almost as funny things as fed AP poppy. still, he is not OP in that way, one silence, one stun, one of those things i wrote kills him.
Mordekaiser is a beast, yes, if you let him farm that 800 AP, you can do nothing.
But imagine what would a Brand with 800 AP do. Not Mordes fault you die all the time, only your own.
Pretty easy, isnt it?