Not to mention attunement for progressing after Kara. I would say that was probably another part of the downfall for it. The difficulty in anything after Kara would be the lack of knowledge for the encounters. Those two things alone were defeating itself.

My first guild ran Kara for a YEAR. Solid year. 6 hour raids. Horrible, epic fail. Why were they so bad? Well, the raids were poorly organized, so that a 25 man never got off the ground (plus the RL didn't want to do 25s). The poor organization turned into lackadaisical raids, that would take half hour breaks while the RL was smoking, trash clears would be so bad, by the time we got to the boss, the trash respawned. Finally around 1am-2am the raid would really get rolling, and we would churn through a few bosses. At one point we got up to netherspite at 3am, and I had to quite. RL and all that.

Anyway. When ZA came out, it was like 'great'. But that guild could not do ZA, it was not geared enough. Now, wrap your mind around this. Even after farming Kara for a freaking year they weren't geared enough. Since we didn't do Gruul/Mag we didnt get the rest of the tier pieces, and we didn't do much heroics, plus 2.3 didn't drop, so the badge rewards were only t4 level mostly. Anyway, if that experience is any indication, most guilds could do kara but that's about it. There was really nowhere to go beyond that, due to numbers and skill required.

My second guild, on the other hand, started fresh, and we blew through kara, quickly doing full clears in about 2-3 hours. (Oh, this was another big difference, the second guild actually read up on the fights and didn't mind wiping to figure it out; the first guild had the attitude of 'nope, we're not good enough for this). Anyway, we blew through T4 within a month, and the next few months we did T5 (this was when 2.3 hit so we could do those kara runs and get BT badge gear. T6 was right around the corner and we did MH in a month and spent another month or so on BT. At that point, wraith release was announced, and we know the big nerf was incoming. We got all the way up to Illidan and had a week to learn him before the great nerf. We didn't get there, the wind went out of our sails. After the nerf we quickly downed him plus all the other bosses that gave us trouble; Vashj, KT. I think we did get archi down though (that guy was really not that bad). Illidan back then was the absolute monster of raid bosses (appropriately), much like LK was extremely difficult for raiders to figure out.

Anyway. Cataclysm is another beast. I haven't done any raids in cata yet, due to time constraints and heroics being a royal pain in the ass. I think that pretty much killed my interest in doing end-game content, that the heroics were just so challenging. Now, I like challenge, i'm a hardcore gamer, but I don't like spending 2 hours in a freaking dungeon for which i'll get nearly nothing. Wraith was different, at least you'd get a ilvl200 epic at the end. Not here, nope. You'd have to run a single dungeon about 20 times to get a valor item (not 20 times in a week thanks to the valor cap, more like 3 weeks. So, the ability to get appropriate gear is really hit hard, its hard to get into FL when a single piece of FL gear would take you typically 3 weeks of really heavy heroic running.

In contrast, battlegrounds are pretty easy and straightforward, so alot of my guildies are turning BGs, including myself. I dont really like PVP but it's easy, so that's the main appeal for me. I just don't have time to run...7 heroics a week, plus 3 raids or whatever.

@Rob:

You don't need to be in full valor 378 gear to do Firelands. A couple weeks of heroics should have you in mostly 353/359 gear, and that is plenty to do Firelands. Our alts run regularly goes 6/7 post-nerf with most toons having 353/359 gear.

Certainly the transition from 10 to 25 was part of what made things difficult, but I believe there were other factors in BC as well. Mag was a bit overtuned for its place in the raiding, Blizzard acknowledged this later and nerfed it. Past Gruul and Mag you had attunements (at least at first) so that certainly had an effect. And finally I think the bosses on average stepped up the difficultly level after Kara, though you certainly had easy bosses in each tier (Void Reaver, Lurker, etc.). At the time, other than a bit of badge gear, you had to gear up with the raid to get to the next raid. This was before the Wrath "only the recent tier is current content model." It has harder to overgear content and so later content was not done as much as early content.

It does raise the question of what a better raid model is. The Wrath/Cata model or the Vanilla/BC model.