So, basically, Mass Psychosis gives the opposing units chance to attack their master/mistress, eh? Unless you say otherwise, I'm going to assume that those 'traitorous' units are affected by effects of the shield their master/mistress wields ... which may lead to funny results when an Elite Psion decides to turn coat and strike at their master without knowing they're holding a Mirror Shield or something (but good luck finding Psion and Mirror Shield, let alone Jade Shield, in the same deck).
Also, I'm curious how does Momentum (since Momentum normally makes the unit ignore opposing shield effects) and Adrenaline (Adrenaline basically gives the unit multiple attacks; does the chance affects each attack or the entire volley?) interact with this shield, upped or not.