Ah, however, the domino field is also effective (albiet partially) against units with the Preferred Enemy rule, and units with even better rules (Kharne). While we're at it, I'd change the ruling so that rather than being effective half the time (a lot of pointless die-rolling), D-fields and special to-hit rules cancel each other out. IE the unit hits normally (with it's weapon skill halved, as per the holo field), instead of hitting on a 3+ with it's own rules, or hitting on a 6+ as per the D-field