well NOD has what you call " GDI counter technology" they dont have very powerful units aside from the avatar which when fully upgraded, can match if not stop a mammoth tank rush.
I like GDI, not just because they are the good guys, because they have this awsome bull rush mentality. sure you could spit out more scorpion tanks than you can predators or even mammoth tanks. NOD is all about rushing. it takes a very long while to build up a sizable force/ excellent base defenses, but once you have a fleet of mammoth tanks, pitbulls, zone troppers, mcv's with infantry and snipers and at least 2 squadrons of orcas/ firehawks, youll rip a base easily, i can care less if you have a crapload of obilisk of light around your base.
the key trick to doing well with GDI, is to turtle. there is no point in rushing a base only for a bunch of small units to be decimated and have barely anything to stop a counterattack.
here is how you counter NOD units
flame tank---- zone troopers/ preds or even mammoths( get the railgun upgrade even if it cost 5000 units.)
avatar---- definately mr. commando and orca's.. mammoths can help out too.
scorpion tanks----- a crap load of missle troppers in mcv's/ zone troopers and tanks
nod buggy---- thats stupid for me to answer, my slingshot can kill it
nod infantry=-- very difficult to deal with unless you have snipers./rifleman in mcv's.. and yes i hate those nod fanatics,, i get irratable bowel syndrome every darn time i see these fools.
stealth tanks--- any good hitting unit with stealth detection will do.
venoms/ vertigo bomber---- ill let my pitbull or even 2-4 squadrons of firehawks armed with missiles turn them into chop suey.
the scrin...man are they dangerous, sending swarms of aircraft to the point where your air defenses are too weak= priceless. reminds me of ID4.