To each of his own, I guess. I did not really care which "timeline" I was in. Illidan and Kael'Thas were the enemy in BC. Lich King in WOTLK. And a lot of "zone bosses" and stuff in the Vanilla. I like WoW lore, hell, I LOVE it, and I love reading quests. But never had the "omg, my glass is shattered now" effect from knowing if one zone takes place after another or not. Does not matter to me.
It is unrealistic to demand Blizzard a sudden turn of realism, now TOTALLY changing the face of quests once raid bosses have been defeated, or new expansions released. It is just not a realistic demand, imho. I do not care.
// EDIT: Well, I care in the sense that it is UNBELIAVABLE and FANTASTIC what they have done with Cataclysm. Changing the status que. But I just do not expect them to repeat it anytime soon with BC/WOTLK. Wotlk is perfect as it is. Too bad people will never fully enjoy that with its raid anymore.