Of course there is. It makes perfectly clear that these guys are not the main villain.
A. you dont need to worf the entire magical world to show these are not the main villains, letting Natsu and Gajeel win a close victory though sheer determination ala the battle of FT could have accomplished this without ruining everything else.
B. You dont need to show these are not the main villains because there had been enough things moving around in the shadows to hint at additional threats.
C. You dont need to dedicate an entire chapter to show that these are not the main villains, since revealing the main villain would have done the same thing faster.
There, thats 3 reasons why that was awfull storytelling.
You see, your reasoning is the entire reason behind doing this. You thought the magical world having moved on or Sabertooth being around was plot critical. Turns out it isn't. Showing so blatantly that Sabertooth is not a critical threat is the only way to make sure they are not at all important, just a bunch of overhyped dudes. Does it ruin the build up? Yes, of course it does, that's the whole point of a decoy antagonist.
And i think you missed the collatoral damage from this, seing as it hit not only SB both all the other guilds as well.
And that does not matter, since the tournament is not important at all.
What does that have to do with the tournament?
When i say take on, i mean FT style, with collatoral damage to ruin the entire city in the process.
That is simply not what happened here. Natsu was able to defeat Rogue and Sting. People have been saying they are the bee's knees. The obvious conclusion is that they are, well, not. You're jumping to the conclusion that they are indeed as powerful as advertised and by consequence that Natsu is above everyone else in the tournament. That ignores two key factors:
1) It is very likely they are not as powerful as you were led to think
2) Natsu's power fluctuates wildly
Basically, you're making a big deal out of something that clearly isn't. I understand you not liking it, but it does serve a purpose in storytelling. It could have been done differently but then again, anything could.
Now this is actualy an interesting argument worth close considderation.
And yes, if we take the match alone, then the clear conclussion should have been that the 2 DS's of ST were just simply to inexperienced, due to not having fought the same number of life or death battles.
Unfortunately, we were shown repeatedly and from several sources, that it was in the entire magical world, and though several victories in the guild tournaments, that the DS duo had earned their reputation.
A reputation that was supportet by the rest of the ST team, who generally showed a very solid level of skill, if they had been weak enough to lose to Natsu in a 1 vs 2, then it should have been noticed by the rest of the team, who would have had to carry them though previous tournaments.
1) Even accounting for overblown reputation, if Natsu has not turned into the second comming of Gildarts, then its a huge plothole that he is able to defeat 2 DS's using Dragon Force, the same buff that allowed him to defeat a wastly superior wizard saint.
2)Yeah, Natsu's level of power does suffer from random plot-related jumps, though barring outside influence activating DF, then its actualy not that big of a jump, usualy just barely enough to win.
But the problem here was then that Natsu made it look easy, meaning that its not Natsu"absolute peak of his power" that won, but Natsu"goofing around with his guildies" that defeated 2 other DS's.
But regarding the new chapter, then yeah, it is going to see if the kingdom has anything in reserve to deal with a team like this, who could crush normal castles and armies with ease.
Also, it would be nice to know a bit more about the gouverment of the Kingdom, like if its an absolute monarcy or not, because breaking Lucy out by force (impossible to do it by stealth with Natsu on the team), should make the entire guild criminals, and this most of all leads my thoughs towards the Ernes Lobby arc in OP, where the strawhats declared war on the world gouverment.