User blog comment:IamJakuhoRaikoben/Chapter 482: Vigor, Review./@comment-25111584-20160418195707/@comment-5894890-20160418215426

Erza not being able to beat them makes perfect sense to me. Firstly, she was still injured from her last fight with Ajeel. Secondly, she's fighting 3 powerful foes at the same time, whom she barely beat in past, which arguably is stronger than just one powerful foe (depending on the damage, sort of like Erza possibly being able to defend a torpedo, or 3 people slinging rubber bands, but not 3 people shooting a gun? o_o) So key words here is: overwhelming numbers, and having to diverge or attention. And Lastly, she stood her ground for awhile, and then she got destroyed after a miscalculation (well, kinda)... which in this case, when you're fighting multiple foes, if one mistake is a made, that mistake often leads to a complete down fall, where the others' follow up, multiplying the fatality of the blow.