How does Morde's new ult reinforce his theme?

Mordekaiser's new ultimate is cool as hell, and looks like a lot of fun to play around with. Unfortunately, I'm not sure that it's right for a mace-wielding warlord whose will (whilst alive) was to dominate and slay as much as physically possible, and whose will (whilst undead - if that's the right term for someone in his situation) is to continue slaughtering while also learning much about the realm(s) beyond. I understand the point of him being able to manipulate the realms through sheer willpower, and why he might be ABLE to access/create his own death realm to pull champions into, but I fail to see WHY he would bother.

When I think of who Mordekaiser is as an individual, here's my take:

To start, when someone wants to conquer and dominate and control nations as much as he does, they don't take their time killing people one-on-one. Mordekaiser would be killing as many people as possible, as quickly as possible. He doesn't want a single, thrilling fight like Fiora or Jax, he wants to dominate as much as possible. You can't kill people quickly if you kill them individually.

That begs the question:

Why would someone who wants to kill as much as possible care about a single soul? He's killed an uncountable amount of enemies, what makes this next one so special that he might want to take them to a place that they can barely comprehend to do it? Wouldn't he just slay them where they stand and move on? No one should be special enough for that kind of attention from the iron revenant, except perhaps the one who betrayed him.

No one is significant to Mordekaiser. He is such a powerful warlord, he wouldn't bother with the theatrics of dragging someone to the death realm and killing them there; he would simply kill them, and they would end up there anyways. They aren't worth his time.

When I think of who Mordekaiser is, and was, as a champion in League of Legends, here's my take:

-Juggernaut -Big -Slow -One-man army -Do not get close to him -Do not get even remotely close to him -Excels at killing multiple people in close proximity -Excels at pushing waves -Uses the death of those he kills to his benefit -Magic, but will murder you with his mace should you get too close -Unthreatened by ganks (almost prefers more enemies)

Although a lot of these are definitely in his new kit, one thing that isn't here is "1v1 duelist" or "scared of multiple enemies" or "needs protection when trying to kill someone". Why does his ultimate take one person with him, so he can attempt to outduel them without the inconvenience of other enemies? Doesn't someone playing as Morde WANT to have multiple enemies? Isn't that why he has always had so much AOE damage, and a shield that is stronger against multiple people, and the ability to use one kill to finish off anyone he hasn't yet slain?

**These are all questions I wanted answered, and so I watched Mordekaiser: Reimagining the Iron Revenant ** https://www.youtube.com/watch?v=cc0kgY--5tc

In it, the design team says this:

• "[We want to keep] the feelings and the elements that the old players did like about the champion and bringing them forward."

To address the point, the feelings and elements that I have already brought up should suffice for at least some rethinking of why the ultimate may not be a good fit for him. How can League's oldest one-man army continue to be considered a one-man army if he's being forced to duel, 1v1 against other champions? Last time I checked, Mordekaiser would be the last person to send a whole army after one person - that's usually his enemies' job.

I am not saying his ult should be redone, not with the amount of time and effort that went into it. I would just like an explanation that satisfies my questions at least a little bit.

TL;DR :: Mordekaiser is not a duelist, and has never been a duelist gameplay or lore wise. He wouldn't waste his time making one person's death more special than the rest.