User blog comment:Derax-Pagani/Chapter 502 Review/@comment-24102956-20160919112456/@comment-1359322-20160919152425

Brandish didn't screw up, it was shown with Neinhart, a mage with greater magic power than Brandish can negate her magic. August is stronger than Brandish so her magic won't work on August from the start.

So the faults actually lies with Mest, to be specific his lack of planning. He didn't understand what kind of magic August has nor did he understand how Brandish's magic work and just ended up doing something stupid.