Sometime during the Wrath era Blizzard introduced a radical new idea to the game - the LFD queue. I think this came out right when ICC did, but I'm not sure exactly. Regardless, this tool was intended to help players everywhere find groups to run dungeons and heroics with. Now instead of being limited to your guild, folks who were actually in /trade, or your immediate circle of friends - you could let the RNG do it for you, while you busied yourself with another task. Tears of joy were shed by everyone, as the days of standing around in Dalaran looking for a tank, healer, or that last DPS were finally past us.
Within moments the "LF Tank H UK" disappeared from /trade. With the ability to queue for any specific dungeon, heroic, or a random dungeon (rewarding additional tokens/gold/etc), players simply didn't bother forming their own groups any more. It wasn't long before players realized that even with a 3:1 space ratio, tanks and healers were still in short(ish) supply, and that DPS ques were significantly longer. Tanks were able to charge a premium price for an instant queue - I've seen them go for 100g or more per person (20g was pretty standard fare). As players began to significantly outgear instances, the AoE fests we all remember become AoE laugh fests. Heroics were cleared in under 10min, and life was fairly good. Even for a single DPSer, the wait would generally be no more than 20 minutes or so.
The number of tanks and healers continued to rise as the expansion wore on, simply because it was the most efficient way to level an alt. Want a druid alt for the no dismount herbalism perk? Spec feral and laugh your way to 80. Just rolled a brand new DK and hit the Outlands? Spec frost and laugh your way to 80.
The birth of a new era
With the launch of Cataclsym, and a whole new style of dungeons and heroics, the DPS queues have skyrocketed once again. It's not uncommon for a single DPS to wait 30, 40, or even an hour for a queue to pop. I always feel a little bad when I see the LFD pop up and one of the DPS misses hitting the accept button. You know they probably fell asleep, or had to get up an feed the dog. Come back, and poof - you're back at the beginning of the cycle. What's worse for them is when they finally do get to the head of the line, they enter a dungeon 'in progress' and it's falling apart/ending as they get there. Even if they don't get a LFD cooldown, they are still stuck waiting another half an hour for the next opening.
I imagine that a lot of this is stemming from a variety of factors. First, the tanks and healers of progression guilds are back on their mains - and all the tank/healer alts are back on their DPS mains. These groups are rocketing their way to the top, and generally are only grouping together, and not queuing individually. Tanks and healers in this group generally have plenty of DPSers waiting to fill their groups, and it's players they can usually depend on to have a successful run.
Second, we're about two weeks into the expansion. Players who aren't blasting through the content but are instead taking their time are just now hitting the gear/level cap to even queue for heroics. Since they are fewer in overall number, the queue times go up. DPS who shot to 85 and reached the gear requirements are now sitting back waiting for them to catch up.
Third, the dungeons simply take longer to complete. Even if the total number of tanks and healers is exactly the same now as it was one month ago, the dungeons just take more time to finish. I don't know how long we're spending in the average heroic now, but I know it's long enough to get two or three Bloodlusts and Lay on Hands off. This alone is enough to push the queue times up to thirty or forty minutes. Just picking a number from the air, I'd say it takes about ten minutes per boss in any given instance. This includes all the trash, the boss fight itself, and any pre fight chat. This number might be a little low, but it's good for doing some quick math. So an instance like TolVir where you have four bosses, you can probably expect it to take thirty to forty minutes if you don't have any wipes.
Fourth, there may very well be fewer tanks and healers in the general population than there were before. I find this fairly difficult to believe, simply because every guild still needs the same number of each to fill their raid roles. While there's no real call for 5 tanks in most 25 man raids, serious guilds will have their OT/DPS players who are helping get the raid ready through heroics. This of course is a problem that has affected guilds since the beginning. You need 1:1:3 for a regular dungeon, 2:2:6 for a 10 man, and 3:7:15 for a 25 man. While these numbers may vary by one or two healers/tanks for specific encounters, the base is the same. This leads to fewer tanks in that general pool, as those that aren't tanking are probably out doing things to help further their guild.
Finally, the LFD can be downright abusive. Sometimes it's simply not worth the headaches to sit through a heroic, just to put up with a string of asshattery and idiocy. There's still too much to do in the game for this to occupy my time.
The sense of entitlement
One key thing that I believe has escaped most players is that the LFD tool is exactly that, a tool. It was designed to assist you with getting a group together, not provide you with the perfect group instantly. The tool allows you to do something else while waiting for a heroic dungeon, instead of being the one person stuck in Dalaran while the other two DPS are out farming/grinding/etc. It saves you the hassle of dealing with the player who asks for a summons to ICC, when they're all the way in Dalaran (it's soooo far away). All of these things are benefits of the LFD tool, however there is a price to be paid for using the tool - you can't always get what you want right away.
I challenge anyone to be honest with themselves and think about those days before the LFD. When you'd sit around hitting /trade "LF Tank H UK pst", or "2DPS LFG H DTK". You kept a little pocket list of tanks and healers, and you'd always check at the very beginning. You'd ask someone if you could put them on your friends list for future runs. Or for those of us that tanked/healed, it was the "Tank LFG H DTK" and getting hit with 10 invites instantly (especially when they started the heroic daily dungeons).
Fortunately, these tools are still available. You can choose to use the LFD and take your chances, you can look for random members in /trade, or you can generate your own list of players on your realm. You don't have to join a guild or become BFF with people just to group with them, it simply ups your chances. While there's also the option of rerolling/speccing to heal or tank, I don't think you should have to play in a way you don't want to. Unfortunately, this choice comes with a consequence - a longer queue in the LFD.
Right or wrong - this is the way it is right now. It's not going to change any time soon, and I don't really see it as a problem. WoW is a MMO, it's designed to be played with other people. While you can go through a large portion of the content solo, I don't think you should (nor can you) be able to complete everything in the game by yourself. You have to find a group or guild to complete raid content, and I don't understand why the expectation is there that you don't have to do this with dungeons. Cata has already gotten rid of the majority of group based quests to the best of my knowledge, I certainly didn't encounter any as I was leveling to 85.
So while I'm not saying suck it up buttercup, I am saying that I believe it's working as intended.