Hey when you revisit Mordekaiser remember this....His passive is BASIC AF
SInce you have basically stated to the public that Mordekaiser re-work that will be re-reworked can I give a suggestion. Give him back his Armor / MR stats as a passive. I find it weird that he is now a "Juggernaut" but really only because he has his Q and a gimped W that has potential with an ally, but basically an afk skill when there isn't anyone around.
Either his passive or one of his skills needs to have a unit kill stack mechanism like nasus or Garen's re-work. If you are going to make him immobile and have no cc then he has to have a reason to balance that. The solution being well have a strong CC ally is trivial and just poor execution at the basic level.
Give him back his defensive tools to his kit or at least allow these defensive stats to be applied to his shield. A la his HP has 100 Armor but when shield is active it has 130 etc etc. the shield needs some interactive play, something that boosts his abilities when it is in play. This could be a worthy excuse to why he may only need two abilities in solo play situations, his passive and active damage dealing generate options for each skill making them more diverse.
Speaking of his shield its produced by basically stealing the life force from those around him. Couldn't there be some interaction when that shield is broken some consequence to his opponent. Its a shield but really you guys have made it simply extended health it needs to be a shield on its own. Iron maiden damage mitigation something. Make him a Juggernaut not just some slow guy with a massive mace.