Monthly Campaigns

A lot of folks feel that modern MMOs are too grindy. I suspect this has a lot to do with the business model needing subscriptions.
A nice touch that would keep players coming back would be monthly campaigns. Much like the old D&D weekend long campaigns, I'd like to see an optional campaign every month. Mystery, intrigue, and battles with a commensurate prize at the end (not just a title, please).
I understand we already have the MSQ and other quests. The issue is they are the same quests, they are not new or fresh (aside from the new MSQ or seasonals). A monthly Campaign would add freshness and give players something interesting to do rather than monotonous to do.
Look at how popular the seasonal events are!

Before you flame, just think about it for a moment. Every month a unique chain of quests (much like the seasonals, more extreme) to pique our interest. You may say, well we have seasonal events already. Yes and they are fun, however most of them are short, maybe a week long and then it is over with a few quests (although this months looks pretty dang good). I'm proposing something deeper and involved.