When I first saw the Mord rework, I thought his ult was neat. But, now that he's been out for testing, there are things that fully negate Mordekaiser's ult, causing it to do nothing, and going on it's insanely long CD.
Fiora can Parry Mord's ULT.
Olaf can R out of the Death Realm.
Gangplank eats an orange to get out of Death Realm.
Morganas spell sheild causes Mord's ULT to do nothing and go on CD.
Edge of Night spell sheild does the same as Morgana.
Even if you interrupt an ulting Urgot with Mord's ULT, Urgot still kills them while he is in the Death Realm.
Even tho it's not a debuff, QSS is a Get-Out-Of-Death Realm free card.
These are just a few examples of how easy it is to fully cancel and ignore a Morde ult. It seems to still be treated as a debuff, and there are many ways to ignore his ult.
I say make Morde's ult Unstoppable. Where you can't just eat an orange and be ok, where you can't Olaf ult of the D Realm, where anyone with an ANimation cancel can't just cancel your ult (looking at you Riven, Aatrox, and ulting Yasuos), or Spell sheild out of it.
RITO plz, almost everyone cancels Mord's ult