Well, what do you know: Heroic Karazhan --- Free Medivh! in August 2022 , as for apprecitation — for example: Nazra Wildaxe Heroic - 2024 .
Don’t get that ‘flex’ part, I’ve been mostly using or buying such things (card backs, hero portraits etc) to ‘celebrate’ or commemorate something; for example, even though I played only Classic a while ago, when it was still a thing, I purchased the Aranna portrait just because I liked her adventure (don’t remember, maybe I wrote this somewhere, too 
PS Did some quick searching — maybe not?).
But if it’s difficulty or ‘fake difficulty’ that you speak of, then there’s been this problem: Heroic Chess in Karazhan . It still might be much harder than originally intended — dunno, haven’t tested in 2025.
Sounds more like ‘signalling low IQ’ to me. 
Oh, wait, the card back in question is on my list, too, maybe I should be more careful with such statements… Well, no matter, I don’t care about my ‘opponents’ (mostly bots, morons or something like this anyway), really. Although sometimes I do ‘troll’ them with emotes when winning if they’ve been doing it too much during the game — so maybe sometimes I don’t totally ignore them… Well, no matter, still don’t care what they think or feel.
One I’m missing of those three gangs, I think, because that was when I was drifting off from HS…
Dunno about seizures, though.
I was about to say it was almost intended as an unofficial set, but I mixed it up with Tinyfin Beach.
https://hearthstone.wiki.gg/wiki/Morgl_the_Oracle#Trivia
Yeah, something like this — that’s how it is almost intended to be done, I think, and that’s what I was talking about.
If memory serves, many solo adventures have been using such thematic card backs for opponents — I really like such attention to details and care with which they’ve been crafted.