The Devil Walker is a Fallen vehicle that acompanies packs of Fallen. They have strong armour and equally strong weapons making it difficult to take them down alone. It can be seen in action in the E3 demo.
This is laughably easy with a good crew. First, keep behind cover and pick off the smaller enemies – watch out for the Fallen Captains.
Each of you should then take up a position far from your teammates. Facing the Devil Walker from the entrance to this area, good spots are behind the large pillar on the left; in the tunnel on the far right; and in the horizontal tunnel behind a bank of earth right in the middle. The Devil Walker will be constantly turning to face its most dangerous target of the moment, who ought already to be in retreat, giving the other two Guardians time to strike.
You’ll need a long range weapon. Keep your distance, and stay mobile. The boss has two major attacks you need to watch. If his turret lights up blue, move away. If a red targeting laser comes anywhere near you, leg it. (Remember; sprinting will cancel reload actions, and hitting reload or scope will cancel you out of a double jump much faster.) Both of these attacks do splash damage so really put some space between you and the projectiles. The two side positions need to back off further between attacks as they’re more exposed. Just shoot, get behind cover while the Devil Walker fires, rinse and repeat.
You need to shoot the Devil Walker on the legs; it takes very little damage anywhere else. If you shoot one leg enough to break off its armour, the Devil Walker will fall down and its case will open, exposing its vulnerable core. (If you don’t do this, you can still win – it just takes a lot longer.) The two Guardians on the sides should charge in and unleash supers and grenades; if you have a Hunter with you, it’s best if they stay in the central spot, because they can use their super to snipe – it’s easiest to hit from the left bank. Unarmoured legs are not worth shooting, so change targets when you’ve knocked one leg out.
When the field fills with enemies, retreat to someplace entirely safe from the Devil Walker and take them out, then return to continue hammering the boss.
If you run out of ammo check the puddle in front of the Devil Walker’s stage, and the stage itself, where plenty of downed Shanks should provide ammo drops. If the Devil Walker is firing or about to fire at a teammate you can usually nip in and grab some ammo, then go on the lam before you’re hit. If you keep running out of ammo, consider buying some ammo refill packs at the Tower before setting out, or use a slower, heavier weapon.
When the Devil Walker finally falls, the door behind it opens and a number of Fallen Dregs and Vandals will flood out. Don’t let them take you by surprise; this is a hot spot for first timers to party wipe.