On the note of Susano'o: The inverse of your point Bambu isalso just as likely, that Orochi is simply VERY strong for a non-god, like how Cerberus is capable of matching Hercules or Olorun in battle. Some "non-gods" Are much stronger than others and should be viewd case by case. I mean...Look at Scylla. Smashes boats and eats people....vs Cerberus who has several fights against legitimate gods under his belt. Then we have gisnt 8 headed dragon monster who eas known to be feard by the gods. A being who had to be tricked into a passive state before being killed. Plus, Amaterasu, Tsukoyomi, and Susano'o are a trio of god siblings not that dissimilar to the Greek trio. And Amaterasu, and Tsukoyomi back when he was her husband, ruled the pantheon, seriously whats with gods and incest, lol. If two of them are pantheon head material, Susano'o is more than likely not that far behind. Of course the greek trio is likely just a LITTLE stronger since the verse treated Zeus as the KING of the gods in general and even Ra and Odin respected that point. So I'd say ita fair to argue Susano'o as among that upper tier. And before you bother to knock me for using some irl myth material in reference to Tsukoyomi....he is literally coming out this year, so pretty sure implying him is fair game.
As for Fenrir: again, nothing is ever stated about it outright making him stronger during Ragnarok. Yes his ultimate is NAMED ragnarok, but its just an ability name of a creature with natural size shifting abilities. But yeah. His lore, the comic, and even the events like Hera's Odyssey, points where he played major roles in, never once state him to have a drastic boost during this time. Especially considering that, by Hera's Odyssey, all the Ragnarok energy, yes ALL of it, was shoved into the earth by Pele when she ripped what Hades had of it from him, and gathered the rest from across the globe and shoved it into a fissure. The story even states that it was all of it, so Fenrir couldn't have had any of it in him. And his lore outright states him to be an Odin killer, if given the chance. And it did take the combined efforts of Thor and Argus ro bring him down, with Thor shattering his teeth, which, as someone who knows what a broken tooth is like....kind if made me flinch from the thought of it lol.