How to kill Mothrakk from the Like A Moth To Flame mission

Bring a vehicle and use the mounted gun. Either will work, Rocket Launcher is easier but will take more time, Machine Gun is a bit quicker but a little bit more difficult because you actually have to aim it.

While in the gunner seat of the vehicle Mothrakk won't actually fire on you. Cheezy strat (AI Bug), but it works.

For a valid strat, run to the bottom of the hill and take cover under the roof of that building and just pop out to shoot her and pop back under while she shoots fire down. A good sniper rifle is best for this strat. It'll take a while, but you'll get it eventually.

One good way is to hide inside the vehicle station shown in the map (the fire balls won't hit you there):

You go out, shoot and go back inside the vehicle station waiting for the fire balls. And keep repeating the process.

Mothrakk is weaker versus explosive weapons more than anything else. So get a good explosive weapon, hide in the car garage and ping away!

If you're running a Soldier having a nice Ammo Regen mod is also very handy.