Got some help from another post
here
With that in mind I've come to this:
/nb add 3 [Confess!]a:cast:-:e;con:unst:-;st:1::e[Silence The Heretic]a:cast:+:e;con:unst:-;st:1::e[Pistol Whip]con:unst:-;st:1::e
I haven't tested yet, but in theory it should:
Confess! if not caster and not immune (requires parry);
StH if caster and not immune;
Else PW if noone of above and not immune.
Thoughts?