So if I have Rieeken as my admiral can I use Biggs to deal damage to an Unique X-wing (Such as Luke) still in play even though it has taken more damage than would normally kill it?

Yup.

Zombie Luke.

Zombie Wedge.

Necromancer Biggs!

Rogue squadron hasn't escort. I think the reason is obvious. A damage black hole for 13 points would be awesome!