Now I've got the beginnings of co-op over Steam. Looks like I'll have to mess about with predictions, and then sync all the enemy and loot stuff over. It's a shame you can't test out multiple clients on the same pc because they need different steam users.
my gameplay video I hope you enjoy also it's very hard to hear me and I'm sorry the video cuts off abruptly my video screen recorder thing cuts off after 9 minutes and I had to post it through this. it only allows images on my profile.