O.K. this is how it is done,  Have a gauss hog on the back of the pelican and have it fly around the hill bombarding the wraiths and the troops while the troops and the gausses on the ground surround the hill and attack.

2nd idea- duct tape together all of the hogs and then drop them out of the pelican on top of the wraiths so that the hogs and all the gauss ammo explodes and takes out the wraiths, then surround the hill and attack with all your troops.