Back in the old days of Azeroth, before draenei and Outland were retconned into World of Warcraft lore, there was a well-defined dichotomy in the endgame, establishing a clear separation between the “casuals” and the “raiders.” This dichotomy was enforced by poor itemization in the pre-raid dungeons (Boots of Elements come to mind).

Blizzard tried to fix this with 20 man raids like AQ20 and Zul’Gurub, but by the time these raids came out, the player base had established a new cadre to fill in the gap: the “casual raider.” The separation between player type was no longer completely enforced by the guilds, but rather on how much effort the player wanted to expend in order to raid. New guilds were formed to tap into the casual raider focus.

Casual raiders are players who want to raid, but don’t have the time, energy, inclination, or some combination of the three to progress as fast as the hardcore raiders. The creation of this new group was enabled by the dawn of a new age in World of Warcraft raiding, with better itemization in Dire Maul (hello mp5 and +dmg) and the easy slack-off in the huge 40 man raids. Since the big raid guilds had beaten Molten Core and Blackwing Lair, the details of those encounters were well-known. And with 39 other people in the raid, slackers in the casual raid guilds could go afk or die early or whatever, and still get some gear here and there. It was just slower, which was no biggie when you’re getting an epic or two each month.
Oh yeah, I forgot to mention that back then, epics were really, really hard to come by for 98% of the player base.
The pre-Outland raiding scene was limited only by what the specific guilds wanted to do and how they wanted to do it; attunements weren’t really a roadblock. Molten Core attunement was accomplished via a simple Blackrock Depths run. Onyxia attunement, on the Alliance side, was pretty damn easy. The Onyxia attunement for the Horde was difficult by comparison (the elite dragons come to mind) but accomplished with 5 man groups rather than a raid. And the Blackwing Lair attunement was so easy it’s almost laughable: just click the Orb behind Drak after you kill him in yet another UBRS run. AQ20 and Zul’Gurub didn’t require attunement, and neither did AQ40 (I guess opening the gates was an attunement for everyone). The biggest and baddest raid of them all, Naxxramas, required the expenditure of gold for some materials, depending on your rep with the Argent Dawn.
Fast forward to Burning Crusade and we see a whole new raiding scene. Blizzard introduced an entirely new, complex scheme for attunement to raid dungeons. Karazhan requires a fairly simple quest chain that has the nice byproduct of gearing people up a little bit. Serpentshrine Cavern and Tempest Keep used to have a difficult attunement involving running a lot of heroics in addition to completing Karazhan, Gruul, and Magtheridon.
Wait. Used to? What happened?
Blilzzard discovered that the difficulty curve was too great. Guilds were farming Karazhan but having a lot of trouble with Gruul and Magtheridon. Despite the intention in progressive difficulty, guilds were bored fighting the same two bosses over and over and wanted to attempt the higher content. So Blizzard removed the SSC and TK attunements.
The Black Temple and Mount Hyjal attunement chains stayed. Hyjal attunement is straightforward: get the quest, kill Vashj and Kael, get your vials, and there you go. Black Temple attunement is much, much more complicated, involving a deep lore-based quest chain starting in Shadowmoon Valley and taking you through SSC and TK, then Mount Hyjal, where you have to kill Archimonde. You have to complete both tier 5 raids as well as Mount Hyjal to even set foot into Black Temple. It’s long, difficult, and involved quest chain.
So imagine the uproar and excitement when Blizzard decided to remove the attunement requirement for Hyjal and Black Temple as of patch 2.4. The hardcore raid guils are upset that something that is so hard and important is being removed, while at the same time excited that they’ll be able to recruit a little bit easier. Coriel at Blessing of Kings sums up his opinion nicely:
[For] raiders, quality of reward needs to match the challenge overcome. However, it is generally accepted that the first few bosses of T6 content are “easy” and really are not worthy of the quality of loot that they drop. But this is acceptable because Kael and Vashj are so difficult. Early T6 bosses do not just reward you for beating the T6 boss, they also reward you for killing Kael/Vashj.
Essentially, the first few T6 bosses are “reward bosses”. There are other reward bosses in the game: Void Reaver in Tempest Keep, the Chess event in Karazhan, the drakes in Blackwing Lair.
But with the attunement removal, you don’t need to kill Kael/Vashj, so the challenge ceases to match the reward, and thus there’s a lot of complaining. People are allowed to skip the hard content and access the easy bosses with over-generous rewards.
Meanwhile, phoenix_singing gives another perspective about the immediate effect:
This won’t affect raiding any more than the lifting of SSC/TK attunements did. You’ll have more people going in, but you won’t necessarily have more people downing Archie/Illidan. Most guilds who are serious about clearing the content will poke their heads in, recognize that they need the T5 gear, then return to SSC/TK to collect said gear while boosting themselves through the process with loot from the easier T6 bosses. Those are the ones this change will impact the most: the ~3 times a week guilds who are working to progress, who are serious about downing bosses and seeing content, but are moving more slowly for whatever reason. I know my raid alliance has no plans to skip T5 bosses; but for many guilds, it would make sense to go back and face the Vashj/Kael challenge with some early T6 loot.
People in blues and greens who poke their heads in? Will totally get their heads chewed off by the mobs. Nom nom nom. They won’t stay in there (unless they like death :P), so they won’t have any impact on raiding either. :]
Then you’ll have the people who are truly casual who want to poke their heads in just to see what it looks like. If they aren’t serious raiders, it does no harm for them to be in there either. After all, a majority of those casuals who go in are simply there out of curiosity. Some may be interested in actually doing the content someday, but most will pop in, look around, then go back to their normal thing.
Ultimately, I believe making the game more fun and accessible to the larger playerbase is a good thing. I think it’s hard to argue against that.