Hi all:

For Shadow abitlity : "A hero adjacent to this monster that declares an attack must spend 1 [surge] or the attack is considered a miss."
FFg has answered something like this (quote from CRRG): "Abilities that allow a hero to attack as if he occupied another figure’s or token’s space (Cataclysm, Molten Fury, Earthen Anguish, Changing Skins) are not affected by Shadow if the hero performing the attack himself is not adjacent to a monster with Shadow."
In short what matters is the original hero place

now to the point
Black Out : "Play this card at the end of your turn. Until the start of your next turn, monsters cannot be targeted by an attack unless the attacking hero is within 2 spaces of them."
I suppose the same rule applies here and for Cataclysm, Molten Fury, Earthen Anguish, Changing Skins if the hero is more than 2 spaces away he can attack (even if his familiar/stone is within those 2 spaces)?

Does anybody have an answer from FFG that confirms/infirms this conclusion. If not do you agree with my deduction ?

I do not see a reason the rules for Black Out would be different than those for Shadow (that is, the actual space matters, not the "as if" space).

That's not flawless logic when it comes to Descent, but precedent is better than nothing. Excepting a ruling (or other precedent) to the contrary, I agree with your deduction.