A few different things add up to his slow reaction
1) he not a front line fighter and with out a battle aura he doesn't have the speed to react
2) the hydra started to move unpredictability, giving multiple positions viewed by his demon eye of foresight (causing his blurry vision the thing happen when he dual Ruijerd after getting the eye
3) he lacks experience fighting in a enclosed space, this inexperience means he doesn't have the gut knowledge when to zig or zag
4) he too close to the hydra but he had to be that close to fire off the flame magic to hit the cut necks before they regenerate
So they go over 1) in the first screw-up, 4) indeed puts him in melee range (but he
was dealing with it...until he wasn't), and 3) doesn't necessarily apply with the arena being as large as it was, even with the hydra being as big as it was. Seems like it took the team some time to get close so that he could block the breath weapon.
2) was
exactly what I was forgetting. His Demon Eye of Foresight acting up
was something that happened before, but only when he was outmatched in speed/reactions. I feel like something like this happened in the
arc, but not in a way that would have distracted him. It's nuts how fast the hydra must have started flailing since the Foresight seems to be happening at what seems to be the INSTANT the hydra starts to move. There's almost no indicator that the hydra is starting to flail
except the Foresight for Rudy, with Paul being able to act to save Rudy from the first hit and everyone else struggling to dodge for other hits. Even vs Ruijerd, at least Ruijerd was already running up to Rudy, so Rudy knew that Ruijerd was going to do
something.