What about the "We don't want champions that hardcounter others" talk?
Champions that generate other units as a main part of it's kit such as 
should NOT be separated apart from them
Yasuo is a literal hard counter to any range skill/Ultimate
So did you pull that quote right out of your butt or do you actually have a link to it? 'Cause no one at Riot has ever said they don't want hard-counters.
Along with that, it's simply a matter of playing correctly against Mord. If you make the mistake of placing your pets before he ults, and more importantly getting in range of his ult when you're a backline champion, then you're countered.
On the flip side, if you play it correctly then he has nowhere to go against you.
try playing illaoi against morde, same thing happens and it sucks.
That's the whole point. Morde steals your stats and disables you so he can kill you. He gains all advantages in his realm, and you get nothing to face him with.
Imagine Lvl 1 Cloud with buster sword vs Safer Sephiroth.
I believe the words you are looking for is counter champion what dont you get?
Hey, at least Vik can stun you with his W that doesn't exist in the death realm.
