D-Shift nerf is almost insignificant. A 2 Cost nerf, when you have tools like Owl and you're fast enough to end games in 7 turns already.
Compare that to nerfs like PDK, which gains 1 cost and loses 2 defense at the same time. If you want to argue about a cheap, effective deck that people play a lot, take a look at aggro sword, it got nerfed last patch too.
It's pretty significant if you bricked and can't pull D-shift early.. but not that significant enough that it offer control deck a way to fight. at least mid-range might be able to do something bout it.
I agree that compared to the over-nerfed PDK D-shift nerf seems really lackluster.. if anything they should fix that owl, at least reduce the stat to 2/2 on evo so it can't be used as effective beatstick to clear the board. If you want to upped the countdown at least make it 5 so that midrange deck could get one or two turn extra to deal with it.
Honestly I think that it has mediocre win rate because it is cheap and players across all tiers are using them. Well built and in skilled hands are quite a force. Besides this is a lovely nerf. It still allows you to end games at 8 with chimera or 7 with old school. With all the boosters like mentioned owl it should not be game breaking. I think they actually wanted to make chain shifts harder to use which imho Issa good direction to go. This months nerfs are actually really well thought and smart. They managed to slightly weaken a lot of stuff instead of destroying whole archetypes.
Staircase : good nerf, not tad bad only unplayable on aggro
Carabosse : Literally change nothing
Sibyl : stat drop, nice, good riddance but still playable
soulsquasher : killed the card function to fill the curve, still good but a definite nerf.
D-shift : Lukewarm, ofc control deck doesn't stand a chance but midrange too still have 50/50 win rates vs D-shift, not much change except that differences between bricking and smooth draw become clearer.
I would say that 2 of the nerf are spot on (Sibyl, Staircase) 1 are pretty uncalled for (SoulSquasher) and 2 are meaningless (Carabosse, D-shift)