[Saxon]

Baalz has a good point. They have a ton of advantages, they are great units. That versitility should not be underrated. The nation is balanced by the fact they have a weak end game, but in every 4X game, the beginning is the most important part. The rush is a very valid strategy and if well managed, will give you a great start over your oppenents.

The only other person who has spoken specifically about single player reports that they do not have the "Heim vs human player" effect, so perhaps my experience is not typical. Still, given that humans have a tough time stopping them, I don't see why the AI would do any better.