If anything, I'd imagine a spooked person having less defence, since they have tunnel vision and panic.
I like the idea of the debuff, but at this point you need to be careful balancing its effect, as you fight Shoos and Shooeys in Casper's encounter - so a significant debuff might make the encounter much more difficult than intended (for level 20s, at level 25 the encounter is much easier, I know that).