I see the living story as similar to how the War in Kryta was implemented in GW1. It evolves over time, because the story is continuing rather than being 100% implemented at day 1. Sure, it means that you need to keep coming back to the game, rather than finishing the story in one shot, but I see no problem with that -- either you're invested in the game and story, or you're not. If you're not, no need to return, if you are, then there's more to do than just the living story.