Ultimately I think legendaries were better when they dropped off endbosses. After all, legendary weapons are weapons of great power, a step above even those things dropped by normal raid bosses. Scattering bits of them in Ragnaros' lair, Molten Core... Defeating Illidan deep in the Black Temple and taking his glaives... Pushing Kiljaeden, Sargeras' lieutenant back into the Nether... THOSE figures could drop truly legendary items. A quest reward? Meh.