There's been a fair bit of discussion about the linearity of the new Cataclysm quests already, but the fact that considerably more quests than before are also mandatory for things other than their follow-ups hasn't got as much attention as far as I can tell.
Using quests as a prerequisite for other parts of the game is hardly anything new. The feature already existed in Vanilla and BC, and we called it raid attunements. I didn't really mind them much myself, because while they weren't without issues, I liked the general idea of making players work a bit for their endgame content.
WOTLK introduced a different kind of quest "attunement": phasing. To get access to the flight paths at Nesingwary's Safari, Crusader's Pinnacle and the Shadow Vault for example, you first had to complete some quests in the area or else they simply didn't exist as far as you were concerned. I didn't bother with unlocking them on most of my alts, but I didn't really mind either since those flight masters weren't exactly crucial to anything else I was doing.
Quartermasters that were hidden behind phasing were a different matter however: for example the aforementioned Shadow Vault quest line was also a requirement for getting access to the Knights of the Ebon Blade quartermaster. That's something I found rather annoying. The quest line wasn't terrible or anything, but the fact that it was a requirement for even accessing the quartermaster just ticked me off. Why make me jump through extra hoops when I already have the required reputation to buy the items? It's not as if they sold anything totally amazing either, why do I have to "attune" myself just to buy a jewelcrafting recipe or a piece of levelling gear?
The Sons of Hodir were even worse if you think about it, because their introductory quest line is much longer, and what with them being the only suppliers of WOTLK shoulder enchants for non-scribes, they were a pretty important faction if you were in any way trying to gear up seriously. Luckily for me I really liked the Sons of Hodir quest chain, so doing that one over and over again wasn't actually a problem for me. Still, the way Blizzard made the shoulder enchants bind on account eventually struck me as an acknowledgement that maybe requiring attunement quests for something as comparatively basic as a vendor wasn't such a great idea.
And yet they gave us Cataclysm. It's probably not as obvious if you're still focusing on your first character and eagerly ploughing through all the new content, but try getting an alt from eighty to eighty-five.
People have compared the new story-focused approach to questing to reading a book or watching a film, and I agree: the problem is, after doing either of those things I generally don't immediately want to read or watch the whole thing again the next day. Likewise I have no particular desire to repeat the questing experience on my alts just yet, but I figured that shouldn't be a problem as there are so many alternate ways of levelling now. Right?
So I start off gathering some experience by working on my professions on an alt, which involves mining. Hm, where can I go to mine these new ores... Vashj'ir is pretty! Except, I can't survive or move around there without having done the introductory quests. Balls. Mount Hyjal it is then. After I've exhausted Hyjal's supply of obsidium and want to move on to elementium I think about going to Deepholm... except that you can't even get to the zone until you're level eighty-two and can pick up the intro quest (assuming you don't have a higher-level warlock friend who'd be happy to summon you or something). Twilight Highlands? Not impossible but still very annoying to get to as Horde without the portal, and again it's something that you can't unlock until you're a certain level and have done a certain amount of quests. I guess that explains why there are so many ore farmers in Uldum - unless you're willing to invest time into questing to unlock all the other zones, there simply isn't anywhere else to go for elementium!
Okay, who wants to level up purely by gathering anyway? Let's do some instances. I open the dungeon finder and everything is locked because I haven't discovered the entrances on my alt yet. Fair enough. Blackrock Caverns is not a problem because you can simply fly there, or alternatively there's a shortcut from Hyjal. Throne of the Tides is a problem again though. Unless you have someone who's willing to summon you, you can forget about doing that one without having quested in Vashj'ir first. Without the Sea Legs buff you'll probably drown before you even get there.
Stonecore suffers from the same Deepholm restrictions mentioned above. Since I really wanted to do it however, I bit the bullet and let Aggra take me through her cut scene again while I tabbed out. The moment I'm down at the Temple of Earth, I fly up to discover the Stonecore entrance... and am still locked out, because the dungeon finder considers my ilevel too low. Never mind that I ran the previous instances for loot and that my old ICC gear is fully gemmed and enchanted, it's not good enough - go do those quests to replace all your gear with greens or else!
So you can waltz into a raid whenever you like now - but you can't access many quartermasters, instances and entire zones without having done the prerequisite attunement quests first. Am I really the only one who sees something wrong with this? I always thought it was worth having to put a bit of effort into unlocking a great raid instance for example, but I really don't see why all of my characters are supposed to take doomed ships to Vashj'ir just to be able to do bloody Throne of the Tides.