UPDATE:
Alliance Destroyers escort some Raptors into a combat zone.
The Scout's Replicate ability allows it to quickly overcome an enemy base.
Hunters provide some aerial support to the weaker Scouts.
Stalkers are the closest thing Nanites come to a heavy ground unit.
A Nanite expedition faces off against Grenadiers and Infantry.
The heavier Stalkers and explosive Suicide Drones devestate the lighter human infantry.
Resistance is futile.
A mining expo comes under attack by Nanites.
Militia can be quickly mobilized to stop attacks.
ADDITION:
And in groups...
... they can be effective.
Gee, I should have built some Autodefenses so I wouldn't need to mobilize my workers.
Although expensive and at the end of a tech tree, Capital Ships dwarf everything on the battlefield.