Riot, if I may give my 2 cents, without any unneeded bashing...
You're very hasty about drastic changes in identity, but very, if not overly cautious, about changes to make them fit in to their old and new designs. What do I mean by this?
No, I'm not starting with the (Former) Master of Metal (Sadly, former. Just keep it as that, don't make him fit in.) I'm starting with Cassiopeia. She was originally, in the hands of her former mains, a poison mage, whom would wittle targets down and break sieges by gradually draining their life with poisons. Then, you at riot had a vision. That her E, twin fangs, should be her new focus, and force the change down. Here is where the problem begins. The first issue is that you forced a change for a champion with a smaller community. A smaller community stands no chance at stopping a rework simply because "this champion is not viable in any way" is the logic the majority of players run by. The mains are sailing on a ship, and all of a sudden an iceberg appears (in which case, would be the rework) which may look like the original but in truth is a doppelganger; only looks are the same. You basically create a new champion that former mains do not enjoy and leave them there. That's the second problem. You leave them there. You are so afraid of buffing the champion or working with their mains (or former mains) to make the champion feel like the old version with a new twist. You are so conservative with post rework help but so radical with reworking a champion, which is honestly beyond me; it makes no sense.
There are good reworks, like Sion, and Gangplank. You took the old abilities and gave them new twists. The silver serpents, the barrels, and the ult with upgrades. That is a great example of what you should do. You took the old abilities, and gave them some flair.
Now, let's turn to mordekaiser. He, like cassiopeia, is now a doppelganger; completely different other than appearance. You said you were going to make him more of a bruiser, with more damage over time, but I, as well as many others, probably didn't envision this. You're so afraid of listening to people's general advice and make some contradictions with some of your design policies (invisible power being the big one here. The W passive is a huge example of invisible power.) You're changing what is left of the old mordekaiser into a new being entirely, a doppelganger of his former self. These doppelgangers, in both cases, are not twins. They are shambles, darker halves of a former light half left behind to rot. These light halves are what the former mains and people who enjoyed the champion try to cling on to, to bring back from the dead. But you don't wish to change anything from your designs, and instead push mordekaiser into the depths. Only a single hand is open for mordekaiser; his title. Even if you change his title in the end, make it something less generic is all we ask.
But instead, keep his old title. Grab Mordekaiser's metal hand and pull him out of the depths. Start reaching out to the people dedicated to mordekaiser and ask what they would change to make mordekaiser more healthy. Ask the general community what they want mordekaiser to have.
Ask the community.
You seem reluctant to listen to this boards, which I understand. But you do realize that you can simply post a survey in client asking if people like x and y changes, and they can vote, or just say "these are bad changes, please reconsider. You have other ways of communicating with us, yet you refuse to use them. You don't need a new client to do this either; just make it a web page survey. The whole Mordekaiser dilemma is a circle jerk, yes, but circle jerks exist for a reason. You need to be more conservative with all of your changes, or more radical. And based on how you reworked mordekaiser, be more radical.
Garen received help while being reworked, and now he is almost the same, a true doppelganger; a true twin with a twist. Mordekaiser is not, veigar is not, cassiopeia is not. You are trying to preserve variety, but you nerfed AP rek'sai when it was deemed "toxic", AP tryndamere when it was deemed "toxic", AP yi was completely removed when deemed "toxic". That is killing off variety, instead of promoting it. These off builds are not nearly as powerful as the normal builds, so leave them.
So I'll just say the rest I have to say here, and sum it all up:
1: Be more decisive. Make changes to a champion instead of waiting it out, because the new reworks are too radically different to "wait out" patiently. 2: Speak to us! Don't leave us in the dark if you want to make a change. Tell us, and we can give our thoughts. 3: Do not abandon mains. They are the ones dedicated to a champion, they are the ones you should try to satisfy. 4: Promote variety in all forms, not kill off ones that are toxic. 5, and finally: If non-mains are dissatisfied with a decision, hold it back. You have all the time in the world to think of the change.
Leave mordekaiser as the master of metal and make him an enemy of the shadow isles, a true king willing to stand up to any who dare fight him.
...Just try to communicate. That is all I ask, that is my 2 cents.
*End rant. Complaints. Thoughts. Whatever this is. *
And if worst comes to worst, I have a favor to ask of mordekaiser mains: Do you remember what his scalings, ranges, etc were pre rework? We can seal it away and remember it for the ages. Don't give up trying though, make yourselves heard.