[@Beloss]
It's generally case-by-case depending on the reasonability of the situation, if taking action simultaneous to the enemy is feasible, and things like that. In this particular instance, outright dodging it wouldn't have been feasible, but making an effort to try and mitigate some of the damage by meeting it with a blow would have been possible, even if a proper attack couldn't be launched in the time allotted. 

[quote]Yes, that monstrous arrow's speed meant reacting to it would be difficult, but at the very least an effort to dodge or deflect it would have been enough to mitigate the force behind it; namely, with the strength that Rostam boasted, it would be reasonable to think that even a hasty attempt to deflect the arrow would at least make it a notably lesser threat.[/quote]