Does WoW actually need to be more addictive?
If, ask the guy in my signature how to do it.
If you mean, it should be more fun, well.. there are so many different playstyles, so many different ideas what the game would make great that i think blizzard should just implement what they think is best.
Who am i to tell blizzard what they should design.
I can tell you what i would like, and that is a larger focus on the RPG part of the MMORPG. Immersion. Meaningful character progression no matter if you play in groups or alone. Professions which are fun to level. All that stuff.