Eileen has some excellent showings, i used to think she was shit too, but looking at it again its clear the only reason she looked as pathetic as she did is cause of PiS, something August suffered from as well.
Breaking Erza's bones with one swipe is one of the best feats in the manga.
Deus Sema, assuming it lands on the battlefield unmolested was hyped to kill everyone.
Enchanting Neinhart to resist a spriggans hax also solidifies her as unimaginably more powerful than the average spriggan, and confirms her as undeniably superior to all except August, even while in human form.
PiS was the only reason Eileen turned into a dragon, PiS was the only reason she turned back into a human after getting sliced by DS magic(despite actually being a dragon) and PiS is the only reason she didnt fly around the battlefield in dragon form nuking everyone.
Her only contender in this tournament is August and the few dragon slayers able to shoot her out of the air(unlikely any of them can do it tbh). In the end like August she was never actually defeated, so we dont even know what it takes to truely put her down.
I don't think PiS is the reason that she underperformed. And actually, almost every character experienced some sort of PiS in this arc. This goes for all the Spriggans and even some of Ishgar's mages.
I don't see why Irene should be counted as a special case, but others are not.
Irene failed terribly in this arc because of her cocky attitude and overconfidence.
She thought Erza and Wendy were going to be easy opponents, so she messed up several times. By the time she realized her mistake, she was already being severely beaten.
At the beginning of the fight, she mocked Erza and boasted how she didn't care about her daughter.
When Erza was destroying the meteor, Irene just stared at Erza's ass in disbelief. She had many chances to end Erza's life, but looked dumbfounded instead because she could not fathom anybody outclassing her.
Same with Wendy. She let her guard down and got owned embarrassingly.
Really, it was all Irene's fault... her feats were simply all hype and talk. When put to the test, her performance was ludicrous.
I may have let it slide if Irene screwed up once.
But she got countered left and right all the way to the end... How am I supposed to defend that BS?
The way I see it, Irene earned her spot quite fairly... she didn't live up to her bragging.
Honestly, if you take out all of Mashima's hype, there's really nothing impressive left... feat-wise...
August is different. He stated that only his mother (Mavis) could defeat him.
And
that was the exact way that he went down.
He beat Fairy Tail's mightiest mage, Gildartz.
The only person he faltered against was Mavis.
And considering that he acknowledged and admitted that several chapters in advance, I see no reason to discredit him.
Irene on the other hand, trash-talked from the beginning and was utterly humiliated in the end. It was ridiculous.