In general, some of the dungeon complexes released with the launch of World of Warcraft took labyrinthine to new extremes. As much as I love it, Blackrock Depths is a positive pain to navigate for a new party - it was terrible before the dungeon finder existed, it's not any better now. Modern dungeons tend to have moved as far away from the 'sprawling mega complex' design as possible. Current dungeons tend to be what I call 'bite sized' in comparison - smaller, self contained wings or experiences that contain between three and four bosses, to be consumed in a 20 to 30 minute chunk of time with four strangers via LFD. It's understandable and even unavoidable that this had happened, but I think there's some wisdom in considering how to have a happy medium between these extremes.
Dungeons like Dire Maul, for instance, saw minimal change in Cataclysm because it was already perfect for the new system. Three wings, mostly self contained (one could previously get from north to west via a tunnel into the library, which was removed) with a reasonable assortment of bosses, tied together by theme yet distinct in terms of what you faced in each. Maraudon, on the other hand, is still a sprawling, difficult to navigate dungeon made worse by the addition of incredibly arbitrary starting locations that the dungeon finder only exacerbates.
Mists of Pandaria has continued with the dungeon as an easily digestible experience, which is in many ways caused by the players - I've heard complaints by players that they don't like to run Shado-Pan Monastery or Stormstout Brewery because those dungeons are 'too long' despite them taking, at most, a half hour to complete. When the players are the ones complaining, there's not a lot of room for Blizzard to really design a longer experience, or a more involved one. I had hopes that the existence of scenarios would make it possible to expand out the dungeon again - not to the BRD level of 'small city that never ends with up to twenty bosses' but perhaps up to six, or maybe seven spaced out more in a space to explore a bit. Something that could conceivably take an extra ten or twenty minutes to clear, perhaps. That seems unlikely with the current player mentality.
This has me concerned because one of the dungeons being redesigned for Warlords of Draenor is Upper Blackrock Spire. UBRS is a nostalgia trip for a lot of us, but when it was current, it was a dungeon where up to fifteen players could go, sort of a mini-raid, and it was a sprawling, massive place. There was no physical separation between Lower and Upper Blackrock Spire - one could easily walk between them, they were within the same instance. It seems likely that this is all about to change - with the Blackrock orcs having supported Garrosh Hellscream (Malkorok was a Blackrock) the Dark Horde which served the black dragonflight (and thus, Deathwing, ultimately) is most likely as dead as Rend Blackhand, meaning that the mountain lacks figures like General Drakkisath and Wyrmthalak. UBRS without the rookery? Without the Beast? I have a hard time even fathoming it. Redesigning a classic dungeon (especially one which was designed when players would accept spending over an hour inside it) is a daunting challenge and I'm very apprehensive about it.
It also has led to some very strange experiences running lower level characters through classic dungeons. Some, like Ragefire Chasm and the Stockades, are remarkably different now, lacking several of the bosses they used to have and redesigned to be up to date with Cataclysm, while others like Maraudon have barely changed at all. Every time we get a dungeon revamp, it changes the lower level version as well, so soon we can add Upper Blackrock Spire to the list of dungeons that play wildly differently than they used to, dungeons like Deadmines, Shadowfang Keep, Scarlet Monastery and Scholomance. Considering what the Cataclysm revamps already did to Stratholme and Sunken Temple, we've basically revamped close to 75% of those old dungeons. If you're an old school player who hasn't run leveling dungeon content in a while, you may not actually know any of it. I know I found Sunken Temple baffling when I took my hunter through it recently - the entire upper and lower sections were gone, completely removed.
As I stated earlier, I understand that much of this is the result of players being unwilling, or perhaps even unable, to commit the same amount of time to the dungeon. And it is a good idea to design for the players you have. But I do think we've lost some fun experiences along the way, and I think Blizzard could take that into account when designing new dungeon content - with the existence of scenarios, LFR and flexible raiding, maybe a few flexible fives could be designed, dungeons that are a bit larger, with a few more bosses, and scalable up to ten players so you could bring a group that's a little bit bigger than normal to tackle them. Back in classic WoW, we had dungeons like Strath, Scholo and LBRS/UBRS which rewarded this kind of play, and it could be a fun and rewarding thing for premade groups to get to play that way again. It doesn't need to reward better gear than other five mans - it's the perfect kind of content to place cosmetic rewards, vanity items, pets and other things inside, because it would be content that you wouldn't put on the dungeon finder for PuG's - make it something a premade group would go do. Embrace the nostalgia you're trying to invoke with Warlords and go retro with the design.
This is of course just one idea, and I admit it's born out of my own rose tinted glasses. A lot of those LBRS/UBRS runs were terrible. I know that. I still remember the day my wife saw her Beaststalker BP get ninja'd by a hunter who was already wearing it, watching the Relentless Scythe go to the tank when I'd been running for it for months, seeing literally dozens of wipes in the rookery. I'm not blind to the flaws I'm ignoring here. But I still feel like dungeons have gotten kind of stale, always the same four or so bosses, always in and out in twenty five minutes. To break that up, we'll need dungeons that are liberated from the design constraints imposed by fast queueing and chain running - dungeons people expect to spend some time in.