User blog comment:B214/Question and Answers 6/@comment-2607:FB90:602B:5C13:E835:4052:FCDA:7AE0-20190202193528/@comment-10330822-20190205072810

Right, but the Dragon King-Class varies between Satan-Class and top-tier Ultimate-Class, that is what we are saying. So someone, like Saji, can be Dragon King-Class, and still not be Satan-Class. At the same time, if Saji improved to Satan-Class, he'd still technically be under the Dragon King-Class umbrella. It's not until you reach Super Devil that you start looking at being Heavenly Dragon-Class, which is the tier above Dragon King-Class.

Vritra's abilities are supposed to help make up for his lack of raw power, so while he isn't Satan-Class like some of the Dragon Kings, i.e. Tiamat, he makes up for it with technique.