Vennie's skill reads:

"While you defend, if the attacker is in a friendly ships (mobile arc), you may add 1 (Focus) result to your roll"

My question is how does this pilot interact with things like a Structural Dame crit, or Wedge, meaning it doesn't roll any defence dice; does you still get to add a focus even though you didn't roll any dice?

Thanks for any insight here.

Yes. You still go through all the steps even if you don't roll dice.