On the Limit Cut thing:
"Towers"
What does "Towers" mean?
It's common jargon. People that do Savages know it. Most people that do Extremes know it. But what does "Towers" tell you if you DON'T know it?
...nothing at all. In fact, I called them "meteors" (like World of Darkness) for the longest time because I thought of it like someone catching a meteor to prevent it exploding from a hard landing on the ground, and many incarnations of the mechanic have a ball slowly descending to the ground as the timer before the mechanic goes off. The first time I heard "Towers" I was really confused because I saw no towers anywhere. I think "Towers" originates from Coils (going to say Nail's fight, but I forget which one) where there are circles on the ground but they also have little Alllegan monolith things (like the stones in the PvP map Seal Rock) in the middle of them, and the monoliths were called "towers" for short. But honestly I don't know. "Towers" says nothing meaningful at all to a new player that doesn't know what they are, and isn't even DESCRIPTIVE of them, since almost no modern incarnation of the mechanic has the monolith structure to be a "tower" in the middle of the circle.
And yet, the name stuck, didn't it? No one goes around telling people "Don't call them Towers!", because everyone's kind of just accepted the meaning and that the general definition of "Towers" is "circles formed on the ground in the arena that require either one or two (or rarely 4) players to stack on them, often in some combination of Tank/Melee Healer/Ranged-Caster before the timer on the mechanic expires".
"Limit Cut" is the same thing. Yes, there's a "well ackshually" behind it, but there is for Towers, too. And "Light Party split" (though at least that one KINDA makes sense from the name). And the name of that thing where doritos have to stack together to not take damage (never remember the name of that one, but you know the one). Or the "get away (often) Tank targeted AOE" that we call "Flares" even though most versions of it aren't "flares" at all, it's just that was what it was in...what, the Megadeath fight, maybe? The one with the giant head? Clearly you aren't getting angry at people for calling that mechanic (the blue arrows pointing three directions away from the target signaling other players to get away from them before it explodes) "Flares" even though they "aren't flares", right?
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I kinda hated the name Limit Cut when I first encountered it myself (which was DiamEx) because it describes literally nothing of the mechanic or how to deal with it, but I've accepted it's the term and know the general meaning - something to the effect of "places a number of dots from 1-8 on players and then does a wide cleave attack targeting them one by one in that order which often places a debuff on them but will basically kill any player caught in two of them, and will require some form of player cycling through designated spots of being hit to prevent cleaving the party and causing a wipe" - just as I have for "Towers" and "Flares".
You can fight that battle if you like, but I'm not sure it's a hill worth dying on. I still call "Towers" "Meteors" from time to time (and people understand what I mean by that, too) or "Everyone get to your circle", which works just as well, but I recognize the community accepts the word/term "Towers" for that mechanic.
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Plus side on those is "Point blank/PB AOE" and "Doughnut" describe the first two well and are both often used and entirely descriptive. I don't hear Protean often, I usually hear that as "targeted cleave" or, in the cases it's on all party members and everyone goes to their clock position, some variant of "death pizza".
Agreed on those being some of the changes (that you mentioned), too.
This could be part of it, but note that WoLEx and HadEx both were regarded as the MOST DIFFICULT Extremes back in ShB. I think WoLEx was the last one I actually cleared (thankfully got an EXTREMELY uncharacteristic for me luck of getting the mount on the second clear, so while I did it a few more times with the party until everyone was ready to stop, I didn't have to do it AFTER that - I did it so many times I was literally typing mechanics in /party by the end of it. Think I spent...15 or so hours straight one Saturday? I was determined to get that clear! And that was after having spent the evening Friday on it. Just took a while to get a party that could get the mechanics, and every time we got CLOSE to a clear, someone had to go and we had to train a new person all over again - THAT is the PF experience, btw, and why Extremes shouldn't be like Savages...). So suggesting that's "the same difficulty" doesn't really speak to it being standard for Extremes since you're comparing it to arguably the most difficult Extremes at patch in the game's history. Ones that, at the time (and by people today) are often considered Savage level of difficulty (especially HadEx at level, but WoLEx is right there with it). And as you noted, was before people could cheese the gear a bit.
So if BarbEs is like that, then that IS Savage level difficulty.
I'll also note that, like BarbEx, WoLEx was a favorite of...the raiding community, who felt it was a "challenge" to them. Meaning more like Savage and less like Extreme, not to put too fine a point on it.
Though I highly disagree with this:
Presumably, by "getting better" making them easier, I'd have felt that HydEx was easier than TitanEx. I felt the exact opposite. I also felt BarbEx was harder then RubEx.
The fights have gotten harder, and BarbEx isn't "the normal level of difficulty", as you're comparing it with the most DIFFICULT Extremes in the game's history, not the normal. Normal Extreme difficulty would be something like Ruby WEAPON or Susaku maybe. It's not "people who became used to the easy content". Other than WoLEx and HadEx, which I did have to come back to, I did all the other Extremes in ShB at level in ShB. I've also done all the Extremes at level (including Endsinger) here in EW. The EW ones all felt harder to me other than RubiEx. And if we've "gotten better over time", I should feel the opposite way.
The implication is, despite getting better (and I have), the content/fights are also harder, and harder enough that even me getting better feels like they've gotten more difficult than the gap of how much I've improved. If I improved from a 5 to a 7, they got harder from a 5 to a 8 or 9.
Sorry, but I generally hate the "stuff is easy, people just got lazy/used to easy" counterpoint to literally anything. It's ALMOST always false, and in the rare cases it has truth to it, it's often missing some nuance that is important and makes it not so cut and dry.