they're not really ignoring them, they just haven't seen them.
seek and destroy means they wander around looking for trouble. put a cylce WP next to it otherwise they will stop eventually
guard is best used in conjuction with a trigger type switch. a group on a guard wp will head to any part of the map where the enemy have been detected.
check the tutes for more, there's plenty on this kind of stuff, particularly in Getting Started.