User blog comment:Miskos3/Fairy Tail 511: The Hell of Starvation, Review/@comment-24546844-20161119172808/@comment-2214433-20161119173430

On the other hand, it's about fucking time Sting and Rogue started showing that they can do something. If the 5 dragon slayer children are having a hard time against humans, how are they supposed to stand against Acnologia one day?

This is why Sting and Rogue losing to Natsu like that back then fucked everything up. Admittedly, they did manage to do something against Mard Geer later and even defeated something that Mard Geer hyped up to be stronger than the 9 Gates, but hey, trusting Mard Geer's words isn't the best thing to do, right? ;)

Even if we ignore the past, given that Rogue is literally destined to fight Acnologia, he shouldn't have had any trouble with Historia Spriggans.

In other words, if Mashima actually thought about power levels (he doesn't), Sting being able to take on Larcade would make sense, because both of them are supposed to be able to fight Acnologia. Well, eventually.