No. It's a lot more complicated . It is scaling from the World of Darkness [ I thought before it was the Gentle Darkness... I was hella wrong ] being stated to be one half of the full Universe, as well as contexual evidence it created everything within it , which in GX , 5D's , and DM has at least 3 timelines . It also makes sense how Nightshroud knew a lot about everything... He was involved with the Creation of Everything, since he is the World of Darkness .
GX scaling :
Nightshroud also played the card called " Creation of the Universe ", which acccording to the wikia was meant to literally be the power of the Universe and being the symbol of how the Universe was . They always have sources for their claims at the bottom of the wikia [ Which is why i'm willing to quote them more than other wikias ] so i shall recheck it at a later time .
This would also mean the Spiritual Power of Nightshrouds' deck would be 2-C by that point because it contained such a card , plus the World of Darkness [ Which by itself is Possibly 2-C ] , plus all the villians from before in GX . Here are some notable quotes :
- When the universe was created [ Unknown by whom. likely Numeron Dragon ] , it split into Darkness and Light { HEAVILY implied to be the World of Darkness / Gentle Darkness and Light of Destruction .... Nothing else fits unless you're referring to the Gentle Darknesss, which would still make Nightshroud "Possibly 2-C" by default and still allow the Gentle Darkness , Yubel , and S4 Judai to scale to it . } [ Yu-Gi-Oh! GX episode 155 ] . Keep in mind only S4 and above GX would scale directly to 2-C .
- This card is referenced in the Duel by Dartz in Yu-Gi-Oh! meaning the timelines are definitely connected here, and GX and Waking the Dragons... Are actually canon to each other.
- Yubel is able to resist Nightshroud's power, when Nightshroud has his base power [ World of Darkness + ALL the previous villians, including the Full Light of Destruction ] . Keep in mind that Nightshroud removed Yubel's spirit , so Judai and Yubel were far weaker than before. They should scale easily to Nightshroud once together, because once they were together they oneshotted him . Post-Season 4 should be well above Nightshroud by an Unknown margin.
How does 5D's [ Signers/Dragons ] scale ?
- Bonds Beyond Time shows us the power of Judai's spiritual Deck post-Season 4. It wasn't capable of defending against Malefic Stardust [ Litterally just a bloodlusted Stardust, even just using game mechanics shows us his attack power never changed in that form ] and nearly killed Judai and Yubel if it wasn't for Neos. Keep in mind both Yubel and Judai took spiritual blows against Nightshroud. So everything scaling to the Signers and the Dragons scale to "Possibly 2-C" as well as the Signers , even BoS, being 2-C via scaling [ Because Stardust never got "stronger" , he just has stronger forms , which he didn't need against Judai ] .
How does the original Duel Monsters scale ?
- Yugi Mutou : Stated to have the most powerful spiritual deck in his Battle City variation [ Both GX and Bonds Beyond Time heavily support it { Yami oneshotting Paradox Dragon , a monster Stardust was struggling with } ] , which obviously would scale him to Nighshroud and post-Season 4 Judai . Since Yusei had the Full Signer Dragon inside of him and used it in the battle, and BBT takes place before the True Graduation Duel , this would mean Yugi Mutou's Battle City spiritual deck is well above that of the Full Crimson Dragon, which was used later to bring about Shooting Quasar . Shooting Quasar is many leagues above Shooting Star, and Shooting Star is well above Stardust power-wise . This would make Waking Dragons Arc Yugi and Atem well above that level, as well as everything after Battle City .
Scaling :
So the scaling is like this : Yugi's [ Battle City] Spiritual Deck [ Stated to be leagues ahead of EoS Yusei by Konami according to a What-If Duel between the, ] >>>>>>>>>> Shooting Quasar >>>>>>>> Shooting Star >>>>>>>>>>>> Stardust >>>>>>>>> Post-Season 4 Judai >>>>> EoS4 Judai >>= Nightshroud . Also supports the fact is that in a What-If duel posted by Konami between Shooting Quasar Yusei and Yugi from Battle City, Yugi curbstomped and was stated to be leagues ahead of him.
Conclusions
Any questions... Sorry it was so long. I need to get my thoughts together before making this. And yeah i have a blog on this, but i need to edit it to replace G.D [ gentle darkness ] with W.o.D [ world of darkness ] .