"There is a pervasive myth that making content hard will induce players to rise to the occasion. We find the opposite. " -- Ghostcrawler
"The bit about hardcore players not always caring about the long term interests of the game is spot on." -- Ghostcrawler
"Do you want a game with no casuals so about 500 players?"
Yes but look at the bigger picture. It's FUN to also do something that was an actual accomplishment. Getting something for free from a lootbag is not fun for a lot of people so at the very least it's very subjective because there are definitely people that would love to see the difficulty never changing (unless it's a bug fix) and you can't deny that (because that'd be like saying I'm lying about what I want).
You have not bothered to think about what you are saying. If something is an actual accomplishment (as in, difficult in an absolute sense), then most players will not accomplish it. You have satisfied a tiny "deserving" slice, at the cost of cutting the game's economic throat by leaving most customers dissatisfied.
"There is a pervasive myth that making content hard will induce players to rise to the occasion. We find the opposite. " -- Ghostcrawler
"The bit about hardcore players not always caring about the long term interests of the game is spot on." -- Ghostcrawler
"Do you want a game with no casuals so about 500 players?"
You're thinking only with absolutes that's why you're missing the point. Yes some people will find it hard and not do the achievement at the same point in time compared to being nerfed but if they know they downed it with the "true" difficulty then they will feel more proud and feeling proud is very fun.
Sure some people will never down it that way but that's where it becomes very subjective because many others will have more fun that way.
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Also you must bring proof for this claim or it did not happen. I have gone through various semi-hard core and semi-casual raiding guilds in my life and almost never in a true hard core guild (ok only once), and I'm pretty certain every single one of them (even the very casual raiding guilds) had at least 10-20% of the players feeling bad that they kill something that is nerfed.
The people who care about the "accomplishment" of clearing raids pre-nerf are the ones in active raiding guilds clearing the raids from week one. Very few people would brag about killing N'zoth for the umpteenth time in pre-patch and next to no one who's returned for Shadowlands will bother to progress through Ny'alotha, and the ones that do certainly aren't doing it for the prestige of killing normal/heroic N'zoth "pre-nerf".
The pre-patch nerfs have mostly been to let people bring alts through and give returning players a shot at the current content without a massive gear grind.
My point is; you make a good argument against nerfing content mid-patch. But you might be the only one who's still chasing accomplishment 3 weeks out of a new expansion.
Just do what I do just pay 800k and get carried to zoth mythicc for that mount everyone hates - no reason to even worry if the game gets nerfed
On Topic / Fun Aside: I do indeed remember when I was VERY NEW at the game and we struggled a ton until the pre patch hit, back in TBC we started STEAM ROLLING through TBC, I think if I had to guess it had to of been a SOLID 10-20% nerf to everything inside of BT, we were struggling with just a few boss's then we killed Illidan right before launch of Wrath (Boy we felt good, even if we were scrub lords on some unknown server)
Moving forward pretty much everything started to get more open and available, with server hopping and things making the game so easy in Wrath, mega servers started really making pugging a thing with gear score just made WoW the best.
tl;dr I think the nerfs at the end of the xpac are there for people to get one chance at the mounts or that final good feel you get when you try so hard and got so far - even if in the end it never really mattered
they did gut nya'lotha, the only people that are regressing are the guilds that were hyper carried by corruptions, but it's 100% easier than before, because the game was already not balanced around corruptions, so they nerfed it ontop of nerfed it
Nyalotha was nerfed on a weekly basis with cloak resistance getting higher. Another nerf was when the first guilds cleared it, then it was nerfed after the squish. If a guild still can't kill Nzoth, they're just not cut out for it at this time and need to improve in Shadowlands because that boss is a rollover now. It has been 8 months already.