I missed this post until now, somehow, but all I can say is that I'm sorry, but I don't agree with the OP. For me, any game that has single-player should also have coop. If you want my detailed, thoughts, here they are:
http://christophermpark.blogspot.com/2009/05/case-for-co-op-games.htmlIt's something all our games have had day 1 public release until this one, and it's something that gets more painful to retrofit the longer we wait. At any rate, by now most of the major surgery is already done, and multiplayer is working internally with one client connected to its own server, but we're working on optimizing it, etc. A good game design for this game needs to also be able to take into account both SP and MP design considerations, and right now all the MP considerations are on-paper or theoretical, which is part of why we wanted to do it sooner than later.
Anyway, as you've seen with the last little while, despite our sinking a bunch of time into getting MP fully up and running and optimized, it's not like stuff grinds to a halt on SP content. And it's not like it ever would -- as much as I believe in co-op content, I believe just as strongly that all the multiplayer content (player interaction aside) should be available in solo play. So don't worry that you're going to get left behind!