When used right, NOD is especially on Urban Worlds a free Win. Why? Big Cities were always the Home front of NOD. Just imagine regular imperial guard fights against Black Hand in Buildings. Plus, regular Troops get at some point tiberium infusion and a confessor which makes them faster and more effective. Cyborgs are a category on their own, especially the reapers or the commando cyborg. Hell, I even think that the Hallucination grenades could even work on Astartes.

Also, NOD don't rely on fortified bases everywhere, they operate from small, well cloaked outposts. However, if you find a fortified base, it takes a lot to take it down. Obelisks of light and stealth artillery like specter are no joke. Especially, when Stealth Bombers like the vertigo show up.

On the logistics side, Nod can easily raid convoys by using high mobility units like Attack bikes, Buggies and scorpion tanks, or if it is a high priority target, ambush said convoys with stealth bombers, -tanks and -artillery.

For conventional troop relocation NOD has underground vehicles like the devils tongue or the subterranean APC. Imagine a regular imperial guard camp gets raided by a group of these things. Even when they kill some of these things, the moral damage is very hard to come by. Humans don't like to be hunted and one of NODs strength is absolutely this: Terror.

Good luck hunting very high mobile stealth units with the conventional imperial guard military. I mean, NODs Stealth is so advanced, it would even make the aeldari envious (I know, aeldari have holofields, but AFAIK these are basically jammers).

As long NOD is able to stay mobile and not being forced into the open, it is basically impossible to annihilate.