The story of Coil is simply lore (which we admittedly need more of in the main story, but I digress). You don't need to know it to understand the actual story, you can completely skip Coil and it won't have an affect on you at all, it just fills a gap for those interested in finding out about it. Think of it like... a sidequest in most games, where you learn about the world but it's not really stuff you needed to know. It's essentially a sidequest locked behind raid content, which I think is fine, because if raids don't have any relevance to the world then they just feel detached and boring. I don't think Alexander will be any different, but I feel like less people will complain because it won't be about the Calamity and instead it's own story.

Also, this exists: http://wowwiki.wikia.com/Icecrown_Citadel_(instance)