BC lootista ja intansseista(mithan @ vgn):
Loot Progression:
These are my "opinions" based on speaking to people in-game and taken from my own experience.
-Zul'Garub is essentially "green loot" at level 60.
-Tier 1 Molten Core loot is basically surpassed in Hellfire Citadel, though you will lose your set bonus when you start breaking things up and due to people "rushing" in leveling, they may keep Tier 1 a little longer but theoretically, you could run HFC over and over and replace all your tier 1 loot at level 60. Because not everybody has top quality MC loot for every equipment slot, a LOT of quests and green items will probably work out better for you as well. In some cases they wont.
-Tier 2 loot is sometimes surpassed in Hellfire Citadel, but in general, you need to go to Coilfang Reservoir Instance in Zangarmarsh to start replacing Tier 2 and BWL loot, which you can start doing at 63. Theoretically, it is possible to farm Coilfang at 63-65 and basically replace all your BWL loot with better loot I guess but I dont see many people doing that. In other cases, Tier 2 loot could remain around a little longer...it will depend on how much you do instances.
-Tier 3 loot gets replaced at level 67'ish+ instances. Some times sooner and sometimes later. By level 70, Tier 3 loot is essentially equal or less than level 70 Green Loot from what I am seeing/hearing but some of the level 70 Blue Loot is equal to the best purple loot out of Naxx so its hard to say and it varies.
Unless they change Loot Itemization, ALL existing Raids in Retail WoW are obsolete the day the expansion goes Live, but...
MC will take the hardest hit because it has been around the longest.
BWL and Naxx will actually still be "decent" as an "event" for guilds to run while people are progressing to level 70, however there will certainly be much better loot available out there once people surpass 65 or so, but until then... it will be a great run for large guilds who want to keep their raiding sharp.