...This.
The original BRD and BRS took minimum two hours to fully clear until they finally split them in Cataclysm. Ruins of AQ...I can't remember if that was originally a Raid that was converted into a dungeon like BRS.
Sunken Temple, BRS, BRD, Dire Maul, Uldaman, WC, Maraudon, Scarlet Monestery (all four wings), RFK, RFD and BFD (Black Fathom Deep in Ashenvale) are all in out of the way locations plus you need to fight your way to the dungeon entrances, some with elite mobs guarding the way. Stocks (in Stormwind) and RFC (In Orgrimmar) are not easily accessible if you are a member of the other faction outside Dungeon Finder.
...I remember those days of running into Org and hoping people didn't corpse farm me. So glad I don't have to think about that anymore on Retail. On Classic and TBCC you have to be max level at minimum.