You need 2 players. Play through the mission normally, until you get to the bit when you have to open the big door and kill the hunters.

Shoot the bad guys of a revenant, then get one person to get in it, open the door and then use the revenant as a ramp to get the warthog over the concrete wall.

You can also use the warthog as a ram, by putting it side on and reversing the revenant over it.