|Gruul's Lair (1)||Obsidian Sanctum (1)|
|Zul'Gurub||Magtheridon's Lair (1)||Eye of Eternity (1)|
|Onyxia's Lair (1)||Zul'Aman||Vault of Archavon (1)|
|Molten Core||Serpentshrine Cavern||Ulduar|
|Blackwing Lair||TK: The Eye||Trial of the Crusader|
|Ruins of Ahn'Qiraj||Mount Hyjal||Onyxia's Lair (1)(2)|
|Temple of Ahn'Qirj||Black Temple|
|Naxxramas||Sunwell Plateau||Icecrown Citadel|
(2) Recycled Instance
As for my footnotes, I am very well aware that Gruul's Lair had 2 boss encounters and technically EoE has 4. Furthermore, I'm also aware that VoA will soon have 3 bosses. But I believe it is fair to lump them into one category and compare them because they're much shorter instances. If you want to talk about environment, you could even consider Trial of the Crusader as a Single Room Encounter, which meant a heck of a lot less work for the graphic designers. lol.
Further clarifications: I put a space between UBRS and Zul'Gurub since UBRS was still 10-man (down from 15 at a certain point) and Zul'Gurub being a 20-man instance seemed that it needed more coordination and "raid" tactics.
All of that said, Blizzard did a lot in the first few years of Wow. They created 9 classes (8 playable by each faction). They created 2 continents, 24 5-man instances, and 8 raids. Not too shabby. Granted this was all work done from alpha to beta to about 2 years and 2 months until the next expansion came: The Burning Crusade. They then gave us another continent, flying mounts, 16 5-man instances, and 9 raids. Then about a year and 10 months later, Wrath of the Lich King came. So far, we know that they have given us a new continent, 13 5-man instances, and 6 raids with 2 more (Onyxia's Lair and Icecrown Citadel) on the way.
Of the 8 raids in Wrath, 2 of them will be completely recycled from Original Wow. Honestly, I'm completely okay with that. I don't think a lot of people (as a percent of the whole) got a chance to run Naxx or, to a lesser extent, Ony before TBC came out. So, it's good that people now get to go back and see these fights. Especially with Blizzard's redirection that everybody should be able to see raids, it just makes sense.
Albeit, I recognize that there's been less development time, but if you factor in that these 2 instances got recycled from before, the true number is really down to about 6 new instances. And 3 of those are Single Boss Encounters (4 if you count Trial of the Crusader).
Now, I'm not saying that any of the Single Encounters are bad instances. I'm simply saying that they seem like they'd take a heck of a lot less work. And yes, Blizzard has given us these hard mode options to them to make them last a little longer... it's not like it takes them the same amount of time as a brand new instance. If you've been around Wow for a bit of time, you know the excitement that comes with heading in to a recently released instance or raid (bugs and all).
Brand New With Quality
On the other hand, I have to really hand it to Blizzard for Ulduar. It's a fun instance. It really shows that Blizzard has learned what people like and don't like. People like to be able to mount in these huge zones, even if it's just in the first area. Being able to teleport around in Ulduar is also great. Graveyard run times are also greatly reduced. There's a repair person in the instance... at the beginning... and you don't even need to defeat a boss before you repair. It also uses the technology that they've been working so hard on (vehicles) and gives you credit for your awesome gear by making your vehicle stronger.
And from what I hear about Icecrown Citadel, it's going to be more of the same quality. I know it was only a joke, but Ghostcrawler joked that it would have 31 bosses. Even if it only has half that, it's still more than Ulduar has, so I really expect the same level of polish and newness to Icecrown.
But... wasn't that level of polish there in the Vanilla Wow? You know... in the first 8 raids that existed? Or will the trend simply continue and mean that in the next expansion, we'll all be farming Sunwell Plateau as soon as we hit 80?