This seems like an obvious question, but I can't seem to find the answer...

When using the TLT or another secondary weapon that states you get to 'perform this attack twice' -- at what point does the defender roll his defence dice?

a. 1st attack roll - modify attack dice - Defence roll - modify defence dice - 2nd attack roll - modify attack dice

b. 1st attack roll - modify attack dice - 2nd attack roll - modify attack dice - Defence roll - modify defence dice

It is two separate attacks. So 1) attack roll, mod attack, def roll, mod def, if it cancel dice and apply 1 damage. 2) repeat 1.

So whenever a card indicates that you may attack twice, the defender gets to roll defence dice for each attack...correct?

Yes. For each attack there is an attack roll with modifications and a defense roll with modifications.

Thank you for all your help!

Just had a follow up question, I think I know the answer, but I want to be sure.

Say the attacker has TLT.

I am flying the Decimator with Ysanne Isard. I have an Evade token.

The attacker rolls blank, hit, hit.

There is no way I can evade that with a single Evade token, is there?

Thanks!

Correct, the decimator is taking a point of damage from that attack.

(alright, technically speaking, if the decimator is Kenkirk and his ability is active, or the attack is through an obstacle or the decimator has a stealth device, or some other way for it to have a defense die... but you were implicitly excluding those options)