As I said in the blog, we already accepted and added the relation in source of power between Nero, Dante and Vergil (Rebellion and Yamato), they share it, meaning Nero going to 6-C and managing to fight Base Savior is thanks to the same upgrade Dante had in 3, the difference is their base form before that
But since DMC3 Dante has the same physiology, same age, more experience and defeated more relevant demons (the Temen-ni-gru guardians are handpicked demons by Sparda to protect said tower, meaning they are a cut above regular bosses, putting them above DMC4 bosses, which, with the exception of Berial, aren't relevant Lore wise, meaning, Pre DT DMC3 Dante has more or less the same feats as Pre DT DMC4 Nero, worth saying that Sparda knew who Berial was and even fought him), he should likely be on par with him after both having the same upgrade