I've been doing a lot of arenas lately as shadow and sometimes try to use psychic horror as an interrupt when it means we'll get a kill and I think the ability is bugged. What I have seen several times is a mage or druid or any caster class will be casting and I'll psychic horror them, accept nothing will happen. Their cast will continue, they will not get a horror effect, or disarmed. This happened many times in 2s with a rogue partner, and threes with a warlock and shaman as partners.
I am over hit cap as shadow because of misery, shadow focus, and some hit from gear (7.6% hit with all three up) and my spell pen is 136.
Has anyone else noticed psychic horror just not having any effect sometimes? It is like the fear bug where sometimes you fear and you get no resist or miss, just nothing happens and your spell goes on cool down.