If the Avatar is the primary target and It's facing her, then there's no margin of error for the ability. Worms are stationary, and face their attacker, so it's not like a Dragon, or other multi-directional attacking enemy. Like is said before, If him readying his ability counts as 'looking away', because his face is looking up technically, then it's about timing. But if the target is immune to either/or status, it may also effect the overall ability. The only reason I say this is because of his immunity to silence. Still, I took the ability into dynamis and was able to have it apply to the mobs there, as they are still classified as NMs, that was my major test. It doesn't apply to them using their 1hrs, As the HP drop is their trigger, but I know that the amnesia is still in effect, because it prevented a SAM from using any of it's TP skills after it's 1hr was used.