They are meant to move randomly around the map when they are not chasing any units.  That means they can bump into outposts and external resources and raze them.  However I don't think they should be able to try to move onto an outpost when there is a unit on the outpost.

That would make a custom faction with Master Scouts and the Monolith trait Enchanters (which give Arcane Monolith and elemental spellbooks) too powerful.

custom factions can be atm in general too powerful!!! as it stands now, we can create a custom faction with TWO OP-Abilities (like masterscouts and henchman for example)! 

What I don't like is the fact that wandering monsters can destroy all buildings except the outpost itself, and that the AI can take over the outpost.  It's as though the outpost is a physical building--but only to the enemy AI; while to monsters, it's invisible.

I'm thinking the UI really ought to prevent picking two of the racial traits, they should be in their own selection box. "Pick one of these", then move on to next customization.