Yeah, with the increased speed of leveling - they all but killed doing lower instances when they brought out Burning Crusade. When they added Wrath, lol - they did kill it.
As far as what SWG had/has over WoW, just give Blizzard time - cause face it, WoW is just a collection of ideas from many other games (some watered down and a tiny few improved).
Course, talking about SWG made me laugh as I thought about having a pair of buildings in the 'burbs of Stormwind. One of them being a shop, with female halflings, night elves, draenei, humans, and dwarves wearing fleshwraps and talking to me each time I entered...
...I think the Surgeon General would have to place a warning on that, lol.
I still say my perfect game would include elements of Shadowbane, Anarchy Online, Eve Online, Star Wars Galaxies, and World of Warcraft.