Continued from the topic here:
The subject of Dire Avenger.My understanding is this:
1) Generally speaking, each unit may only attempt each psychic power once per turn. This is clearly specified if you look at the rules for the psychic phase. It very clearly says that a psyker can't try to cast the same spell more than once in a turn, and Smite is no exception. This restriction applies generally, not just in matched play. Take a look under 2. Psychic Phase > 2. Make a Psychic Test:
http://whc-cdn.games-workshop.com/wp-content/uploads/2017/06/Warhammer-40k-Battle-Primer-English.pdf -- this is true in both Matched Play and in regular play.
2) Matched Play places an additional restriction on top of this. In addition to each unit attempting each psychic power once per turn, the Psychic Focus rule says that each power other than smite may only be attempted once per turn, rather than once per caster per turn. This means that, if you attempt Fortune with one Farseer, you can't attempt Fortune with a different one in the same turn.
So, under normal rules, you could cast this set of spells:
Farseer 1 - Smite, Fortune
Farseer 2 - Smite, Fortune
and this would be allowed. However, having one Farseer cast Smite twice or Fortune twice would not be allowed, as you cannot have one unit cast the same spell twice.
Under Matched Play rules, you can't cast Fortune a second time. So you can do this:
Farseer 1 - Smite, Fortune
Farseer 2 - Smite, Guide
and this would be allowed. Smite can also be cast by the second Farseer because he is a separate unit from the first farseer, but it cannot be cast twice by the same Farseer, as stated in the rules for the psychic phase. There is no indication that Smite is exempt from the restriction of "a unit cannot attempt to cast the same spell twice" anywhere in the rules. Fenris apparently thinks the following set of spells cast would be allowed in matched play:
Farseer 1 - Smite, Smite
Which seems to me to be unsupported by the rules.
I'd be eager to hear what others have to say on this.