One of the new tactic cards in the expansion has the following text: " ... resolve your after the Imperial player?"

What is the advantage of doing this? If you were the attacker, you could have a little more insight in how to apply your damage. But to be honest, it doesn't seem that useful compared to others.

Am I missing something obvious?

The disadvantage with attacking first with the expansion is you don't get opportunity to remove damage on the first roll. It just gives you a chance to save some ships you may not have been able to otherwise.

Let me know if I am confusing your statement with a different tactic card.

Yes, it is as @centralx says. It's a pretty big advantage to go second. @Admiral Theia (who also liked her/his statement) found that out yesterday, when we played Rise of the Empire for the first time yesterday.

I did SOOOO much worse in a battle I would have won handily in the base game because of going first.