User blog comment:Derax-Pagani/Chapter 509: Kagura vs. Larcade Review/@comment-3285005-20161108025138/@comment-99.13.69.171-20161111233850

Escanor is the strongest there isn't in his verse, I will not deny that. I also will not deny that holy can have some effect on unholy beings, but for arguments sake the opposite can be true with some unholy magic.

As for the whole Sting, Rogue and Juvia thing, first the Dragon Duo, it is natural to save your trump card for last, and it is possible that they trained to get stronger, one Guild Card states that Orga trained insanely to become stronger since the GMG, so it should not be hard to believe those two would do the same.

And as for Juvia, I would be questioning that too but then again, I would say she is naturally reacting to incoming attacks, while her water body does provide some defense, it is better to avoid an attack which you have no idea what sort of magic effects it could have. This was most likely because of her battle with Meredy that she realized that there are some magics or certain circumstances that can counter her own.