Before I raided anything in Vanilla WoW, I had watched a few videos (mostly movement heavy ones with bosses charging random members around). In Vanilla, threat was a real issue. Especially for Horde side, where we didn't have Blessing of Salvation. Old school raiders still remember the saying wait for five sunders. Threat is now just a buffer for some classes (MM Hunters come to my mind) but mostly ignored by all but the tanks.
Most bosses were in fact immune to taunt. They would often charge random members. Shit would loose apart. DPSers had often access to much more damage than they were bringing to the table, but were limited by their threat. There wasn't an illusion of a fantastic tank protecting and keeping you safe. Even in Burning Crusade, many considered Blessing of Salvation to be the greatest DPS increase. It all changed in Wrath like many other things.
Fights we had in Wrath were mostly the "Tank & Spank" kind of variety we old schoolers called them back in the day. Not only most raids in Wrath had bosses with no kinds of adds -or adds that were just the same as the raid elites like Razorscale or Thorim- Karazhan's second boss was Moroes, and it was an achievement to down him. High King in Gruul's Lair was also a fight with a lot of things going on. KT Council, Illidari Council, Vashj so forth were benchmarks of Burning Crusade raids.
Flashforward. Back when Faction Champions were released, it seemed most guilds had a setback, even if only temporarily. Almost all guilds were one-two shotting Northrend Beasts, and Lord Jaraxxus was "merely an interesting fight". But Faction Champions really turned the tides and got some guilds wiping.
People were crying about how they had to do PvP for PvE. It was the biggest nonsense I ever heard.
I really enjoyed people changing specs, taking out certain trinkets for others (Usually the PvP trinket, though sometimes some whacky engineering trinkets did come into play), how abilities unused in raid instances was something valuable (When was the last time you sheeped something in a raid setting let alone a raid boss?). As a DK, even though I was one of the highest DPSers in the guild, my job was to make sure Rogue, Warrior, DK or pets were not disturbing the healers. Hungering Cold, Death Grip, Chains of Ice, Taunt were the skills I spammed the most. I would also Strangulate the healers whenever it was off the CD. People actually bandaged this fight! Everyone understood it was an encounter of survival and they treated it as such.
My only sadness with the fight was, the hard mode was not significantly different, aside from higher numbers and less room for breath. But still the encounter was just a fest!
It made people realize, they had to get out of their comfort zone to kill this boss. You had to learn a new ability, a new skill. In certain cases, people used different gear or even completely different, niche talents for this encounter alone. This is why this fight was one of the benchmarks of Wrath.
When was the last time you've seen a DPS class come to a raid with two different talent builds, even gear, to kill a boss? Hell, back in Burning Crusade, we had two different gear as rogues -one for bosses, well-over the yellow hitcap, and one for trash, with a lot of Agility/AP. We didn't really actively build the second set but it was just a by-product of all the loot that was laying around.
People have to realize that this sort of dedication is what's required of them for hardmodes in Wrath. In most cases, the numbers are so off the chart, you literally have to do everything you can. This is why, 25-men normal guilds have an A-Team of 10 men hardmode raiders, mostly composed of officers and co -because they know they can trust each other. When we were doing Firefighter in 10 men, we once had to invite a random priest from guild, not been in our hardmode runs before. We explained him the fight, wiped a few times before he asked "Why are we bothering to do it? Normal is much easier."
I'm often calm in raids and I can wipe a full day and a half without complaining about repair bills, but people had to calm me down after he said that. We had a guild who was pestering the officers (us) for lack of progress in 25-meh hardmodes, and they were the ones who threw towel after two full wipes. "I don't have the gold for repair bill soz".
This is what the Faction Champions taught -you couldn't rely on the rotation buttons, DPS, Healer or Tank. You had to get creative with your abilities, you had to think outside the box -and this wasn't even a hardmode fight. This was the 3rd fight in the instance, you just had to do it. People can complain about hardmode fights and how they were not cut out for the job, but very few people would like to admit they wiped on Champions and called it a day.
I really hope such fights in the future that greatly rely on people increasing their skills and their train-of-thought will be implemented in the future raids of Cataclysm.