I just checked and behemoths can't reach it to make significant damage. It seems like overkill, but I have repeating blocks of three guns, four laser turrets and 4 flame throwers. Each set of guns is fed with a requestor chest for ammo and each subsection is in range of my bots for repair. Just the wall itself is 6 tiles deep, 2 tiles deep for a plain wall and 4 for "standoffs". It's been impenetrable so far.