Pre-rework Morde was a literal joke* and we cannot revert him to that state
Right now, Morde has high damage, good defense (based on your build), and no mobility.
As opposed to mediocre damage, mediocre defense, and no mobility before the rework. Ergo, the rework improved Mordekaiser as a champion, but made him completely overbearing as opposed to completely underwhelming. Now that he can actually be a threat at all to the enemy team, the problems he would have had pre-rework (Q is the only significantly different spell, everything else just getting buffs of some sort) if he wasn't a chump are starting to show.
1: If you can't shove a lane faster than he can his laning phase is basically free (unless your jungler ganks enough) 2: Most/all of his counterplay in a teamfight is "Damage Morde before he walks into the teamfight."
The new problem with trying to fight Morde is thanks to his Q. "You can't really prevent him from getting that 1000+ damage basic attack ready, so he has a nuke on his right click pretty much whenever." Overall, these create one large problem. Mordekaiser is bound to win under certain conditions, and it's incredibly easy for him to force these conditions on the enemy team. Balancing Morde should focus on enough strategy into his kit so that he can keep the raid boss feel without a coordinated party of 3-5 being the basic requirements needed to defeat him.
With this in mind, the following are a few ideas for nerfing Morde without changing him. 1: Mace of Spades' damage will only get the damage multipliers if Morde is attacking an enemy champion or epic monster. Otherwise, the second and third attack will do the same damage as the first. 2: Siphon of Destruction no longer provides extra Iron Man shield when hitting enemy champions (the increased shield for dealing damage to enemy champions remains). 3: Spells cost increases by 50% if Mordekaiser does not deal damage with that spell (health taken after the duration of the spell ends).
*I mean it. If you weren't around or forgot or something, people were mocked and shunned for playing Mordekaiser. The "BR Morde huehuehue" meme is based on the idea that people from Brazil are bad at video games, so naturally they would play the worst champion.
