actually, mordekaiser can tank 1-2 tower shots with his shield, so he can walk right up to a minion wave under tower and blast both the champion and the minions, then walk away without losing any hp
mordekaiser's only real weakness...as it always has been...is being outdamaged to the point that he can't raise his shield (the new bottom lane wombo combo pairs prevent this so long as he shuts down either the support or adc or both)
or his ability to be ganked to death in top lane
his W was actually a small but important part of his top laning kit, now equally replaced with a free even stronger than his last Q on solo hit ability
he's not optimal, but when he can chunk 70% of a tank's hp when building tanky, he has clear strengths and his kiteable nature isn't much of a weakness with the right support
then champs like quinn/teemo top, he can eat them alive because they have no durability, and that was the old mordekaiser...this one deals roughly the same damage and even more in close quarters, so a flash initiate(well, against teemo since quinn will probably E away) or any of the other ranged tops will pretty much force them to return to base