You are greatly overestimating his nerve. He's not like Alaira, he has no experience, only talent. He can react just fine to opponents. I suppose I should've worded it better, but it's not that he's slow, it's that he's not fast enough. Coupled with the fact that he's essentially hysterical, and the fact that the other guy is summoning 'things that should not be', he can't mount an effective counter-attack. He'd have a fighting chance if he could fight them calmly and efficiently, but he can't.