don't know... i think you may need to follow the breifings a little better and understand your role.
Take out the GW/P's first, they pose the biggest threat at the beginning of the mission since none of the TIE's have been lauched at that time. After you finished them off, go after the TIE's.
Also don't forget to take out the shuttle. One of your commanders will warn you once it is launched. After that, pick of the remaining TIE's (if any).
remember the idea is not to go for kills or points but complete the mission.. noce the mission is completed, THEN you can have fun and rack up points