Hmph... so it appears they fixed the FAQ to back me up.

"Perform this attack twice"...

When you see that sentence you are reading it as: "Perform TWO attacks",

When I see it, I am reading it as: "Perform this ATTACK (singular) twice (repeat the procedure)".

In the rules, during the combat round, it says you are to perform one attack against one opponent [exceptions: Corran Horn's pilot ability, Ghost/Phantom title cards... ]. The upgrade cards for TLT and CM are both "a single attack with repeated procedures" (i.e. doubling the output).

Cards like GUNNER,LUKE or others that "After an attack..." have to wait until the full effect of TLT and CM has been applied before activating their effect. Apply this logic as the intention then all the cards make sense as written. GUNNER would have to have both rolls on TLT or CM to miss in order to activate.

They did more than fix the FAQ, they rejiggered a bunch of rules to make that happen.

^but most importantly the FAQ was released solely to prove Sentinal right. Everything else is just collateral damage.

The game resolves in an order of simple steps.

Simplest way I can think to define "Immediately" is you resolve it before you begin the next step.