Are you sure and confident regarding point one and could you point to any source ? Cause this seems incredibly strong to me considering it's a 5" blast :/
So, the rules for 'And by the manner of his Death did the Emperor judge him' say "All fighters under the marker suffer an automatic Str 3, Ap-, D1
HIT" (italics on
HIT for emphasis). As the action causes a
hit, you must follow the rules sequence for resolving a hit. Once all fighters who are hit by this blast are determined, the next step in the sequence for resolving hits caused by Blasts says "Follow steps 4 and 5 of the Shooting sequence as normal for each fighter hit, in an order of the attacking player’s choice." Step 4 is "Target is Pinned."
Now, this could be argued to be a "Rules as Intended" type of situation. As this attack doesn't have an actual weapon profile like an actual ranged weapon (and, therefore, no
Blast weapon trait), it
could be argued that the blast caused by this Article of Faith skips that step as it causes an automatic hit on anyone under the template. The target becoming pinned actually comes
before resolving the effects of the hit.
However, I do think that this is just one of those classic mistakes by GW where they just assumed that "it was obvious" how it should be resolved. For the record, my gaming group treats it as an attack with the
Blast trait and so it pins anyone hit by it. If your opponent(s) disagree with this ruling, the best thing to do is either ask the Arbitrator for an official ruling or if the situation comes up in a game, use the good ol' 'roll a d6' method; 1-3: It pins / 4-6: It doesn't pin. Then just use that result for the rest of the game/whenever you play that particular opponent.
tl;dr: RAI -
Blast attacks
do cause pinning but, as the attack doesn't
technically carry the
Blast weapon trait, it could be argued that it doesn't. House rule it.