Hi Andy – welcome to the H8000 !!
Computer problems are hard for us to diagnose, especially as the problems may lie in some area that is totally beyond our ken. But, a few things to try.
First of all, forget Logic for now, and set your Mac up so that the Default Input and Default Output both go to the H8000. Do what you have to do to get this working on both input and output. You will have to deal with numerous Routing and configuration issues. For example, in the routing you mention, the 4 audio inputs appear on FireWire1 channels 5-8. If you don't notice this or can't connect to them, you'll get no audio in.
Once these are working as CoreAudio in and out, then and only then should you move to Logic. A caution – any further problems will probably be Logic or Mac related, and not things we here can do much about.
