You have a better webway than the Elder or 'make a coat' people (humies).
They also kill the shit out of enemy morale, while they kill the shit out of anything that isn't a building or tank. You've got 1/3rd of the entire requisition of a Necron army on call at a moment's notice, on attack or defense.
No strategic point is safe, but all of your's are. They're heavy infantry (or were in vanilla), so aren't susceptible to the same things assault scarabs are (light infantry still?). Every 1 1/4 minutes you can teleport 2-4 entire squads of troops at anything your scarabs are doing.
